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Orbit 1.8 User`s Manual

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1. 1999 09 04 Tutorial Rotational Muscle Force g o 1 9 2 Total Longitudinal Muscle Force g o 6 9 0 Contractile Muscle Force gq 4 4 9 0 Elastic Muscle Force gq 4 2 O 0 Similarly we opened the Mechanical State Viewer for upgaze and adduction 15 30 and saw that SO elastic force was 2 3 g Then we used Both Eyes Live Eyes to tuck the SO by changing the LSO tendon length from 20 0 mm to 10 0 mm L50 Palsy PstOp sim 0 POY B Live Eyes Muse Insert Movement around mm from normal forward Muse Insert Rotation 7 Tendon Length mm Tendon Width mm Looking again at the Mechanical State Viewers we found that downgaze showed only a modest increase in LSO elastic force to 3 5 g up from 0 3 This is why the tuck had little effect in downgaze In upgaze LSO elastic force increases substantially to 9 5 g up from 2 3 g resulting in a larger corrective effect in upgaze Thus we see that tucking the SO in this case should not be expected to correct reading positions and why it should not In a different case the pre operative simulation might have included LSO atrophy abnormally low elastic force In such cases we would find that an LSO tuck also fails to correct upgaze 1999 09 04 62 Orbit 1 8 User s Manual Plan a Treatment continued These patients actually were treated with RIR recession of about 4mm and LIO myectomy or recess
2. Help Not Enough Memory suggests things to try when Orbit or any other Macintosh application makes this complaint Help Bibliography An annotated bibliography of scientific papers in which the biomechanical model underlying Orbit the basic research supporting the model and some clinical applications are discussed Help Ordering Orbit tells how to purchase Eidactics products 1999 09 04 A Biomechanical Approach 17 A Biomechanical Approach to Strabismus Clarification is one of the aims of our biomechanical approach so it would be ironic if a mysterious physiologic system were simply replaced by a mysterious computer program It is important to understand something about the foundation and inner workings of Orbit The most important thing for you as a user to know is what is included in Orbit s calculations and what is not A biomechanical model such as Orbit is minimalist in the sense that it does automatically only those calculations that necessarily follow from specified variables and parameters Effects that may occur in only some cases or for which there is no clear mechanism cannot and should not be automatically computed Instead Orbit allows you to explicitly test hypotheses about such effects Orbit includes models of e muscle force including elastic and contractile force components e muscle path including muscle length e Hering s Law which determines
3. e What is the total longitudinal tension in the muscle and how much of it is due to contractile elastic and constant eg externally applied forces e What forces do the muscles exert due to their sideways bending Rotational Muscle Force g ra i at Unit Moment Yector 3 mz nasal 188 188 12 mx Cup 1 1 on my lout 2 1 42 Rotational Force Component g abduct Ta iE H y elevate Hd I a extort H 1 H a Moment Arm Factor of globe radius 166 16g 166 Total Longitudinal Muscle Force gq oH 2 5 Contractile Muscle Force g Dar Goce Elastic Muscle Force q ees 1 4 Constant Muscle Force g HH He HH Ho Rotational Force due to Muscle Width g 6 BHH A BHH H Hai Total Longitudinal Muscle Force g Total Longitudinal Muscle Force is the total force exerted by a muscle along its length that is in the direction of its fibers We conceive of it as the sum of three component forces Contractile Force Elastic Force and Constant Force as described above see section Muscle Force Model 1999 09 04 108 Orbit 1 8 User s Manual Rotational Muscle Force g Rotational Muscle Force is the vector sum of moments due to the Total Longitudinal Muscle Force and the Rotational Force Due To Muscle Width Both component moments reflect the local globe radius and Moment Arm Factor rotational force ae moment muscle due to p ae force longitudinal E oei ana
4. i rbit 1 8 Gaze Mechanics Simulation Users Manual 1 Edition September 1999 11 Orbit 1 8 User s Manual 1999 09 04 rbit 1 8 Gaze Mechanics Simulation designed by Joel M Miller PhD written by Dmitri S Pavlovski PhD and Irina Shamaeva MS User s Manual 1 Edition September 1999 written by Joel M Miller PhD Eidactics Visual Biosimulation www eidactics com Suite 404 1450 Greenwich Street San Francisco CA 94109 1466 Orbit 1 8 User s Manual 1999 Joel M Miller All rights reserved Eidactics Orbit and Orbit Gaze Mechanics Simulation are trademarks of Eidactics Visual Biosimulation and may be registered in certain jurisdictions Apple the Apple logo Mac Macintosh and Power Macintosh are registered trademarks of Apple Computer Inc All other brand or product names are trademarks of their respective holders 1999 09 04 Contents Y Contents V Preliminaries 1 What is Orbit 1 Concerning Medical Use 3 What is Orbit Not 3 Is Orbit Difficult to Use 4 Conventions Used in this Manual 5 We Did Not Do This Alone 6 Required amp Recommended 7 Installing amp Registering Orbit 8 Orbit Installation Files 9 Cleaning Up 12 Sharing Orbit with your Colleagues 12 Click for Help 14 Window Help Buttons 14 Balloon Help 15 Help on the Menu Bar 16 A Biomechanical Approach to Strabismus 17 Parameters and Variables 18 Fi
5. Closes the preferences window ignoring any changes you might have made Accepts settings and closes the window Settings are divided into groups each group attached to Z ata W 1999 09 04 Orbit Reference 85 The General preferences tab appears only in Preferences for New Simulations General preferences are settings not specific to any single simulation or window Preferences for Hew Simulations General Sim Align u Param Fit General Preferences Open on Orbit Launch what is Orbit Normal Eyes Intended Gaze Selector Left Eye Ht20 415 VtE0 A157 ne z Right Eye HE30 415 V 30 415 no z Open on Orbit Launch These check boxes determine what happens when the program is launched by double clicking on the Orbit icon It seems reasonable to begin a new Normal Eyes simulation since if you had wanted to begin with a particular existing simulation you could have double clicked on that simulation A new user will benefit from having the What is Orbit window open but will soon want to deselect it Choose Normal Eye Description allows you to create simulations based on alternative normal eyes that you create Sorry not implemented in version 1 8 Intended Gaze Selector sets the gaze angles in a new simulation 1999 09 04 56 Orbit 1 8 User s Manual Open with Simulation All oth
6. Exporting Mechanical States The mechanical state variables available in the Expert Level Mechanical State Viewer can also be saved to a text file for use with another application such as a text editor or spreadsheet with Left Eye Export Mechanical State and Right Eye Export Mechanical State 1999 09 04 112 Orbit 1 8 User s Manual Point of View The Live Eyes and Graphic Eyes displays represent 3 dimensional objects on a 2 dimensional surface To adjust how they are viewed use Both Eyes Point of View Novice level users get a simplified POV Editor that allows them to select from among named points of view Experienced and Expert Users get the complete POV Editor which allows them to create arbitrary POVs and name them for future use with the button Named POVs can be deleted with _Betete_ To use the complete POV Editor imagine you are setting up a camera to take a picture of a 3 D object and that the picture is the size of your Macintosh screen Enter values of Field Roll View From and Look To using either the scroll bars or the numeric boxes Field is the angular extent represented in the picture View From is the point at which you set the camera Look To is where you point it Roll is rotation of the camera around the viewing axis the line joining View From and Look To Press to see a normal eye fixing primary position as it would appear from the current POV When satisfied
7. L50 Palsy Example RLR Palsy Example and Duane Syndrome Examples We will refer to them in the Tutorial section page 47 Existing simulations can be opened in all the usual ways From within Orbit use File Open from the Finder desktop double click on a simulation icon or drag and drop a simulation icon on the Orbit application icon To begin a new simulation from within Orbit select File New When a simulation is open it is listed in the Simulations menu A simulation is open if and only if one or more simulation windows windows referring to a particular simulation are open Thus some simulation window always opens with a simulation see Both Eyes Preferences and the simulation is closed when its last window is closed Certain windows do not refer to any particular simulation and so are not simulation windows These are Preferences Point of View Converter and all of the windows You can have as many simulations open as memory the machine s and yours permits 1999 09 04 A Biomechanical Approach 35 Test of Binocular Alignment Orbit simulates the common clinical alignment tests in which the two eyes are dissociated prevented from seeing the same targets and the E patient fixates with A one eye as the other follows passively In Orbit 1 8 either or both eyes may be abnormal y i fo datt t I i tect oct Ech eth te tt eet ct I The fi
8. Point of Y Yiew Editor Pov i oe PITS pipt riit e HEFER EEJ The Live Eyes and Graphic Eyes displays represent 5 dimensional objects on a 2 dimensional surface To adjust how they are viewed use gt Tools gt Point of Yiew Moyvice level users get a simplified FOY Editor that allows them to select from among named points of wiew Experienced and Expert Users get the complete POY Editor which allows them to create arbitrary POWs and name therm for future use with the button Mamed POYS can be deleted with To use the complete FOY Editor imagine you are setting up a camera to take a picture of a 5 0 object and that the picture is the size of your Macintosh sereen Enter values of field Roll View Eron and Lone fo using either the scroll bars or the numeric boxes Feki is the angular extent represented in the picture View fron is the point at which you set the camera Look Tois where you point it Ren is rotation of the camera around the viewing axis the line joining View Fran and Leak Tel Press to see a normal eye fixing primary position as it would appear from the current POY When satisfied click _oK Existing and new Live Eyes and Graphic Eyes will be shown from the new POY 1999 09 04 Preliminaries 15 Balloon Help Balloon Help lets you point to an object on the screen to find out what it is ES To turn on Balloon Help select Help Show Balloons Then point to an obj
9. Development of Orbit s graphical interface has been supported in part by The Smith Kettlewell Eye Research Institute San Francisco CA The underlying biomechanical model and the physiologic research on which it is based continues to be supported by National Institutes of Health National Eye Institute grant EY06973 to JM Miller at Smith Kettlewell and EY08313 to JL Demer at Jules Stein Eye Institute UCLA and JM Miller at Smith Kettlewell For more about those involved in this project launch the Orbit application and select About Orbit Eidactics Orbit Gaze Mechanics Simulation and Orbit are trademarks of Eidactics San Francisco CA For timely information about Orbit visit us on the Internet at www eldactics com Macintosh Power Macintosh Mac the MacOS logo System 8 Balloon Help and MacApp are trademarks of Apple Computer Cupertino CA Mac and the Mac OS logo are used under license Unix is a trademark of AT amp T 1999 09 04 Preliminaries 7 Required amp Recommended To run Orbit we recommend a Power Macintosh computer which use 601 603 603e 604 604e 750 or G3 or G4 processors Orbit will run on a pre PowerMac sometimes called a 68K Mac because it uses a Motorola 68000 series processor that has a math coprocessor and at least MacOS 7 5 5 but it will run very slowly see page 115 We anticipate that the next version of Orbit will run only on PowerMacs
10. 1999 09 04
11. 1999 09 04 144 Orbit 1 8 User s Manual and antagonistic pairing of muscles It may provide an index of effective EOM innervation useful in studies of orbital tissue healing and plasticity and oculomotor OM signal adaptation During horizontal saccades transducers implanted in the lateral rectus LR and medial rectus MR of a monkey trained to fixate revealed an agonist muscle tension waveform corresponding to the pulse slide step pattern of saccadic innervation and an antagonist waveform that was similar within a scale factor We never observed transient increases in antagonist force at the ends of saccades active braking or at the beginnings Onset of saccadic force in LR preceded that in MR by 1 6 msec for abducting saccades and lagged that in MR by 1 1 msec for adducting saccades During vertical saccades transient force changes were found in LR and MR which were likely due at least in part to globe translation LR and MR forces during fixation tended to be largest with the eye about 10 degrees in elevation and smallest in depression indicating that effective total innervation was a function of vertical gaze or that there was variation in the elastic component of muscle force related to orbital geometry with LR and MR innervation independent of vertical gaze An exponential decrease in fixation force having a time constant of about 10 days was observed after implantation This may have reflected adaptive muscle l
12. 1999 09 04 A Biomechanical Approach 19 Muscle Force Model Muscle force is calculated as the sum of a contractile force an elastic force and a fixed force useful in simulating traction tests in which an eye is rotated with forceps Contractile force is mainly a function of innervation but is also a function of fractional length change or stretch consistent with the sliding filament model Elastic force is a function only of stretch Contractile Elastic Fixed Force Total Muscle Force Muscle Force eg traction Muscle Force Consider a simple muscle resection The mechanics of this common procedure are more complex than you may think but since Orbit understands how eye muscles work much of the complexity is taken care of automatically To simulate resection correctly you need to know what happens automatically and what is left to your judgment A modest resection may only remove tendon Right eye LR Tendon Muse Insert Movement around mm from normal forward Muse Insert Rotation 7 Tendon Length mm Tendon Width mm To perform a 5mm RLR resection you would change the Tendon Length from 8 4 shown above to 3 4 What are the mechanical implications First consider the operated eye fixing When the operated eye is fixing a given position say primary position the RLR will be more stretched than it was before surgery Orbit computes the
13. It differs from the moment of Miller amp Robinson 1984 by the factor a sin which is close to 1 for w 2 Rad small w 1999 09 04 Math 131 From 2 we have h2 M vidi Rad s a Rad a sin o Rad da w ne B Rad o sin a da W B Rad sin a Q cos a 2 7 2B Rad sin G J e a w 2 Rad 2 Rad 2 Rad If the muscle has lost tangency we simply multiply the moment due to muscle width by the moment arm factor 1999 09 04 132 Orbit 1 8 User s Manual 1999 09 04 Annotated Orbit Bibliography 133 Annotated Orbit Bibliography A guide to published research related to Orbit Current Work Web www eidactics com Look here for the most current versions of Orbit software and the Orbit User s Manual and for answers to Frequently Asked Questions about Orbit and Orbit simulations There are also summaries of ongoing research notices of upcoming conferences presentations and summaries of those recently past Feel free to create links to the site and to suggest that other relevant sites link to it eMail jmm eidactics com 1999 09 04 134 Orbit 1 8 User s Manual Overview of Our Research Program Miller JM Demer JL 1999 Clinical Applications Of Computer Models For Strabismus In eds Rosenbaum A and Santiago AP Clinical Strabismus Management cty Philadelphia pub W B Saunders Introduction Orienta
14. expansion D oO a Co landmarks A Contractile Tt stone fi Strength Strength 50o 200 p greteh ve 1999 09 04 24 Orbit 1 8 User s Manual Innervation threshold called offset in the figure innervation sensitivity and contractile muscle strength allow the normal contractile muscle force surface to be customized e Innervation threshold slides the contractile force surface along the innervation axis so that eg contractile force first appears at lower innervations for decreased thresholds and saturates at innervations the same amount lower Eg if you have reason to think that neuromuscular junctions are weakened increase innervation threshold For a simple example change the innervation threshold of a muscle in the following eye Expert Parameter Editor and note in the Mechanical State Viewer that innervation does not change ie the sensitivity of the muscle is affected not the brainstem s output but the contractile muscle force does change e Innervation sensitivity squashes or stretches the muscle force surface along the innervation axis so every change in innervation behaves like a larger or smaller change on the normal surface Myasthenia eg might be modeled by decreasing innervation sensitivity e Contractile muscle strength scales the vertical force axis A large muscle with more contractile fibers in parallel than normal would be mode
15. 410 W420 410 s Ht40 410 w20 410 Ht40 a5 Wao Ht40 a5 Wen H 0 VWt40 45 sa l H 0 W407 45 Ht40 45 WHO amp H O Vso 45 d T H40 A57 W 1999 09 04 8 Orbit 1 8 User s Manual Type 1 The descriptive signs of Duane Syndrome Type 1 are 1 Very limited or absent abduction 2 Protrusion of globe on attempted abduction 3 Normal or slightly limited adduction 4 Globe retraction on adduction 5 Frequently up shoots or down shoots on adduction Signs 1 and 2 and of course the anatomic findings of Hotchkiss et al 1980 suggest that the abducens nucleus is absent or non functional Signs 3 and 4 suggest that the MR branch of the oculomotor nucleus is providing partial innervation to the LR and so producing co contraction R Choose Right Eye Parameter Editor and click the Brain tab Brain Motor Nucleus Connection Weights of nuclei s total excitation abducens 100 T T T T Oculo MF E D 0 Oculo SF T 100 T T culo r IF T 100 T Trochlear T T 100 Oeulo I0 E E E 10 The normal connection matrix above shows each muscle fully innervated by its motor nucleus or sub nucleus weight of 100 and not innervated by any of the other 5 nuclei weights of 0 Think of these connection weights as applied to the motor neurons or at the neuromuscular junction That is nothing about the fixing eye or about yoked or antagonistic muscles is directly chan
16. Deviation Chart amp Notes Box Scrolling or enlarging the Alignment Viewer reveals the deviation chart and the notes box Each panel of the deviation chart shows the same information as the panel of the alignment chart above it except in a different numerical form Deviations of SIMULATED LEFT EYE right fix Deviations of SIMULATED RIGHT EYE Cleft fix exo dey hy per dev excyclo dey exo dey hy per dey exicyclo devy exo dey hy per dey exicyclo dey deg deg deg deg deg deg deg deg deg Type notes here A deviation is a difference between following and intended gazes positive values of exo mean the following eye is excessively abducted hyper means it points too high and excyclo means it is excessively cyclorotated such that the top of the eye has turned laterally Labels on the right tell whether deviation units are deg or prism diopters this is set in Both Eyes Preferences Use the notes box as you wish We use it to document the simulation 1999 09 04 Orbit Reference 95 Live Eyes The Live Eyes window provides simplified access to the most frequently used eye parameters the only access available to Novice Users Experienced and advanced users may prefer it to the Parameter Editor for operations like transposing an insertion since the Live Eyes will show you if you moved in the desired direction Also you see immediately if the eyes responded to your manipulation
17. L50 Palsy PreOp sim 0 1999 04 06 L50 Palsy PreOp sim 1 1999 04 06 150 Palsy PreOp sim 2 1999 04 06 LSU Palsy PstUp LE meas 1999 04 06 L50 Palsy PstOp RE meas 1999 04 06 150 Palsy PstOp sim 03 1999 04 06 150 Palsy PstOp sim 13 1999 04 06 L50 Palsy PstOp sim 2 1999 04 06 Import a measurement file into the lett eye cancet_ open _ R Locate and Open the LSO Palsy PreOp LE meas file Similarly select Right Eye Import Measurements to import LSO Palsy PreOp RE meas into Orbit s right eye 1999 09 04 Tutorial 53 We have locked the measurements files to prevent inadvertent changes so you will see an alert when you open them The document L450 Palsy Preop LE meas Is locked so you Will not be able to save any Changes Do you want to open it anyway Just click Lo and continue We have saved this stage of the simulation as LSO Palsy PreOp sim 0 I Bring the Alignment Viewer into the foreground by clicking or selecting it from the menu bar 1 L50 Palsy Preop sim 0 Alignment Yiewer Fam am whiplash Left Superior Oblique Palsy Dog Gyn nm Pre Op stage 0 Sim Meas ral 14 d29 1999 Norm 199905331 Chart type lancaster Tick rel LEFT EYE fright eve fixing UF RIGHT EYE Cleft eye fixing 40 30 IJ Kr t G a z 2 d J reo mA AB 40 30 z0 10 O 10 20 30 40 40 an 4O 40 S0 20 10 0 10 20 30 40 AB Horizontal Gaze deg l
18. Orbit 1 8 User s Manual coordinate system is turned outward to align with the orbital axis protrude Positive protrusion means the eye bulges out of the orbit Negative protrusion or retraction is more frequently spoken of in strabismus upward The upward downward axis is tilted slightly from the common anatomic superior inferior axis because our coordinate system is pitched slightly backwards to align with the orbital axis Only protrusion retraction is of practical interest in strabismus Rotation is more of a problem than translation and it is a deep problem rotations are mathematically more complex than translations and further these complexities are of an unfamiliar kind Below we discuss how eye rotation is described in Orbit Coordinates for Rotation Any given 3 dimensional rotation can be described with 3 numbers or coordinates by definition There are many correct rotational coordinate systems and to describe the rotation of an object like an eyeball one must first choose a system on the basis of its usefulness familiarity aesthetics or something else It is important to understand that the same 3 D rotational position may have different coordinate values when described in different coordinate systems Two popular coordinate systems for eyes are Fick coordinates and Helmholtz coordinates The 3 Fick coordinates are named longitude latitude and torsion the 3 Helmholtz coordinates are named ele
19. a g en 5 tnan Posterior vaa n Gin MW 6 Striated Mia j MUSCLE W if e fi Tendon To m 3 F Dkr T mitt ion TEM ET orr Tanen EEEn Pore SU a ore EEEE EEEE EEEE EEE a REEE ee ettr Yip SPER Eee ee Ue whet i C T i T amp In the Tutorial section of this manual we will compare simulations of muscle transposition surgery with and without soft rectus muscle pulleys It will be clear that pulleys are significant determinants of extraocular mechanics 1999 09 04 A Biomechanical Approach 33 Again The notion of rectus muscle pulleys has arisen before apparently without the evidence needed to get a fair hearing As recounted by Scobee 1952 Lockwood 1886 described a band of fibers imbedded in Tenon s capsule crossing the posterior edge of each opening and called these bands the intracapsular ligaments He went on to describe several intracapsular and suspensory ligaments later visualized by Koornneef 1983 Ferrall proposed these structures acted as pulleys but Whitnall 1932 flatly stated that there are no pulley bars or intracapsular ligaments and no need for them so there 1999 09 04 34 Orbit 1 8 User s Manual What is a Simulation 2 My Simulation An Orbit document a set of fixations eye parameters clinical measurements etc is also referred to asa simulation We provide several simulation examples in the folders
20. and note the size associated with Orbit In this example Orbit got 4 8 MB when it launched About This Computer Built in Memory 126 MB irtual Memory 129 MB used on Zev Largest Unused Block 5 7 MB amp Apple Computer Inc 1984 1993 ka GoLive CyberStudio 3 1 1 Mac 05 20 6 MB Microsoft Word 19 7 ME Orbit 1 8 6 4 MB Stickies 176K 1999 09 04 Orbit Reference 121 Quit Orbit and with the Orbit icon selected 1 select File Get Info rbit 1 8 Info snow Memory Kind application program Memory Requirements suggested Size 6500 k Minimum Size asoa k k Preferred Size 6s00 Hote Memory requirements will increase by 1 491 Kif virtual memory is turned off As you can see from the Orbit Info window it would have preferred 6 500K which was apparently not available when it launched If Orbit failed to get its Preferred size of memory because other applications were also using memory when Orbit launched quit some of the other applications and re launch Orbit Because of memory fragmentation it might be necessary to Special Restart your Macintosh to make use of the freed memory Look at About This Macintosh Is the Largest Unused Block large enough to meet Orbit s Preferred size If so launch Orbit again If not you may need to purchase more memory 3 If Orbit succeeded in loading at its Preferred size
21. any part of it in connection with a for profit venture unless you receive written permission from us to do so However you are hereby given rights to quote portions of the manual including figures in reviews and for scientific purposes including public scientific presentations provided proper credit is given In written work that might be Miller JM 1999 Orbit 1 8 Gaze Mechanics Simulation User s Manual Eidactics Suite 404 1450 Greenwich Street San Francisco CA 94109 USA 1999 09 04 126 Orbit 1 8 User s Manual 1999 09 04 Math 127 Mathematical Analyses Most of Orbit s mathematical analyses are described in the literature Robinson 1975 Miller 1984 Recent computational developments however have only been available in the source code We will begin to describe new analyses here Rotational Force due to Muscle Width In versions prior to Orbit 1 8 the effect of nonuniform force distribution across a muscle s width was estimated with the centroid shift calculation described in Miller amp Robinson Miller 1984 page 450 451 This calculation has been found to be the cause of convergence problems Solutions could not be found in certain cases 1999 09 04 125 Orbit 1 8 User s Manual We have therefore replaced the centroid calculation with a different method of accounting for the force distribution across the tendon In
22. t total moment force Eo PEF PLT aaa me eee total longitudinal muscle force rotational force moment due to muscle width So long as a muscle remains tangent to the globe it will pull perpendicular to the globe radius and exert all of its force Moment Arm Factor 100 in rotating the eye If the muscle looses tangency with the globe Moment Arm Factor lt 100 Rotational Muscle Force is proportionally reduced 1999 09 04 Orbit Reference 109 Unit Moment Vector The Unit Moment Vector conventionally symbolized as m describes the axis about which a given muscle tends to rotate the eye m is described in a Cartesian coordinate system fixed to the orbital bone see the figure below The components of m are shown in the figure as my my and mz The spin arrows show the rotations associated with positive values of each component Mx up My out mz medial it would not have been correct to reuse the terms elevate extort and adduct because they refer to components in the rotating Fick coordinate system mx My and mz are orthogonal vector components so that the square root of the sum of their squares equals one or 100 Rotational Force component g Strabismus surgeons who think about eye rotations in terms of the conventional Fick coordinate directions of abduction elevation and excyclorotation wish to know how the Total Rotati
23. 2 Sim Meas ral 4 d23 193 Norm 19990351 Chart type lancaster fick rel LEFT EYE right eye fixing UF RIGHT EYE Cleft ewe fixing 40 LJ K t E a zZ d J Tat Ea OM AB 40 30 z0 10 10 20 30 40 40 AO 40 30 40 10 O 10 20 30 40 AB Intended Horizontal Gaze deg longitude Simulation Cycloratation 4 3 In other cases of SO palsy we might need to consider additional changes secondary to the palsy such as 1 atrophy of the denervated LSO that is subnormal elastic force in addition to its absent contractile force and 2 adaptation of the cyclovertical muscles which chronically held at abnormal lengths have adapted by adding or subtracting serial sarcomeres Tabary et al 1972 Williams amp Goldspink 1973 so that their resting lengths are abnormal 1999 09 04 Tutorial 59 Plan a Treatment Now that we have a simulation of the disorder we can experiment with treatments oS Open LSO Palsy PreOp sim 2 and import the post Operative measurements LSO Palsy PstOp LE meas and LSO Palsy PstOp RE meas You will by warned about overwriting the existing pre operative measurements which you want to do Save the result as File Save As LSO Palsy PstOp sim 0 LEFT EYE right eye fixing UP FIGHT EYE Cleft ewe fixing OTA WA oo ea ao AB 40 230 20 10 10 20 30 40 40 aN A0 40 30 20 10 0 10 20 30 40 AB Horizontal Gaze deg
24. 69 pgs 2155 Nakayama K Balliet R 1977 Listing s law eye position sense and perception of the vertical Vision Res vol 17 pgs 453 7 Robinson DA 1975 A quantitative analysis of extraocular muscle cooperation and squint Invest Ophthalmol vol 14 isu 11 pgs 801 25 Scobee RG 1952 The Oculorotary Muscles edn 2nd cty St Louis pub C V Mosby Co Scott AB 1994 Change of eye muscle sarcomeres according to eye position J Pediatr Ophthalmol Strabismus vol 31 isu 2 pgs 85 8 1999 09 04 Literature Cited 153 Simonsz HJ Harting F de Waal BJ Verbeeten BWJM 1985 Sideways displacement and curved path of recti eye muscles Archives of Ophthalmology vol 103 isu 1 pgs 124 128 Souza Diaz C MD 1976 Additional consequences of muscle co contraction in Duane s syndrome In Souza Diaz C MD Ed Fifth Congress of the Conselho Latino Americano de Estrabismo CLADE 1 pgs 93 101 Guaruja Brasil Smith Kettlewell Eye Research Institute Tabary JC Tabary C Tardieu C Tardieu G Goldspink G 1972 Physiological and structural changes in the cat s soleus muscle due to immobilization at different lengths by plaster casts Journal of Physiology vol 224 pgs 231 244 Volkmann AW 1869 On the mechanics of eye muscles Ber Verh K Siichs Ges Wiss vol 21 pgs 28 von Noorden GK 1990 Binocular vision and ocular motility Theory and management of strabismus edn 4th ed cty St
25. Agreement below Orbit License Agreement As an Orbit licensee I agree to be responsible for all uses made of registration keys issued to me and for all uses made of Orbit copies that have been enabled by entering such keys Enabled copies will identify the licensee on the splash screen when Orbit is launched and in the About Orbit box when Orbit is running I will ensure that only one concurrent use will be made of all Orbit Software enabled by each key issued to me whether I install Orbit on one machine several machines or a server I understand that with the exception of the registration keys issued to me and Orbit files containing those keys I may freely distribute Eidactics materials but only if they are not significantly modified and authorship is properly attributed Unlicensed copies of Orbit are for evaluation purposes only Any analyses I perform with Orbit are my property but in published works I agree to indicate the version of Orbit used I understand that Orbit and associated materials are provided as is with no claims of correctness or suitability In particular I understand that Orbit s data and calculations are products of ongoing research and are of unproven validity I understand that Orbit is not approved for medical care and should never substitute for any established diagnostic or treatment planning procedure I assume full responsibility for uses made of any licenses eranted and will hold Eidactics ha
26. If you are using MacOS 8 0 you must also install some system extensions that are included with the Orbit distribution materials see the Orbit 1 8 Release Notes You may also install these extensions into MacOS 8 1 but must not install them into any other MacOS version Your computer must have at least 8MB of RAM available to Orbit and so at least 16 or 32 MB total and at least 256 color graphics No Windows version of Orbit is available or planned It is simply too difficult to support evolving software on multiple platforms This manual assumes that you know how to use a Macintosh The Macintosh Tutorial which came with your system teaches basic Mac skills Your Macintosh User s Manual and Macintosh online Help can also be consulted about basic operations and terminology This Manual also assumes that you know the basics of oculomotility and strabismus 1999 09 04 8 Orbit 1 8 User s Manual Installing amp Registering Orbit Orbit 1 8 cannot open Orbit f simulations created with versions of Orbit older than 1 5 If you plan to work with older ei orbit oy simulations eg keep o 3 your old version of Orbit Morn e Orbit FOY Orbit Be sure to keep Orbit Prefs these four files shown To install Orbit 1 8 on your computer ES If you received Orbit on floppy diskettes drag the contents of the 2 or 3 diskettes to your hard disk n Orbit 1 585 368 Drbit 1 83e4 Orbit 1 6
27. LIF efn hio bef IR Muscle Color Minimum Saturation ol Maximum Saturation Variable Total Muscle Force Files Write FICTs Choose Folder cleared when L Beautify Simulation opens Show The structures selected are shown Muscle Color The saturation purity of the red muscle color is an index of the chosen Variable Pure red indicates the value you enter in Maximum Saturation and gray the value in Minimum Saturation Files Choose to write each Graphic Eyes window produced as a PICT type file in the folder specified Orbit movies are made using a sequence of such PICT files Note that if you leave this box checked unintentionally you will create many unwanted PICT files 1999 09 04 Orbit Reference 89 Checking Beautify increases the resolution of the drawing The LiveEy tab contains preferences for the Live Eyes window Live Ey Live Eyes Preferences Show iLe ipso Mirso ef esr I LLE ALG bef LMR Mi RMR fA Rob yy RLF LIF fio rio i FIR Show The structures selected are shown 1999 09 04 90 Orbit 1 8 User s Manual Intended Gaze Selector It is not necessary to use the Intended Gaze Selector in fact it is not available to Novice Users Gaze angles can be set by choosing an item from the Set Pattern popup list a in the Alignment Viewer DO SSS Entitled SS Fe ean Alignment Yiewer we E Gyn nm sim n E Meas T
28. Manual ES Select File Save As to name this simulation LSO Palsy PstOp sim 2 LEFT EYE right ewe fixing UF FIGHT EYE Cleft ewe fixing OTA HAM ea ti m HE 48 360 24 16 6 1 268 3238 44 AD an HO 48 S6 26 18 d 16 2b se 48 AB Horizontal Gaze deg longitude Comparing simulation and post operative measurements we have a good match The main discrepancy is the loss of vertical range in adduction This is a plausible consequence of weakening both left obliques and the mystery is really why clinical measurements do not show this effect Further research would be necessary to determine whether this is due to central motor adaptation poor clinical measurements eg incomplete binocular dissociation or a problem in the model 3 Now File Close Simulation to prepare for a new simulation 1999 09 04 Tutorial 65 Lateral Rectus Palsy This is the simulation that suggested soft rectus muscle pulleys ES To begin raise your User Level to Experienced select Both Eyes Preferences for New Simulations click the Sim tab and select Experienced This will give you access to the Parameter Editor and so several parameters not available in the Live Eyes Ss Begin a new simulation with File New Import the supplied measurements files RLR Palsy PreOp LE meas and RLR Palsy PreOp RE meas into the left and right eyes respectively and enter some identification RLR
29. Palsy PreoOp sim 0 Alignment Fiewer Fam nm JC amp TS Fight Lateral Rectus Palsy Gyn nm Mean of 3 Cases Pre Op stage 0 Meas ral O14 dlzi 1999 Norm 19990541 Chart type lancaster Tick rel LEFT EYE Cright eye fixing UF RIGHT EYE Cleft ewe fixing 40 m ieaeees So ar seebee TN OTA WAS ea ey Ea AB 40 230 20 10 10 20 30 40 40 ca 40 40 30 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude Intended Simulation Cyclorotation s 3 1999 09 04 66 Orbit 1 8 User s Manual 35 Select Right Eye Parameter Editor US The primary deficit in a complete RLR palsy is by definition the absence of RLR contractility so set the RLR Contractile Muscle Strength to 0 RLR Palsy PreOp sim 1 Contractile Muscle Strength of normal Lo Loo L 100 C 100 C 100 L100 Elactinr Peace le Cteanocth E nf narmalt In the saved file we set Preferences to suppress alerts about solutions not found If you did not use this file you might see such a message now It simply refers to the fact that the paretic right eye could not fixate all the points we selected and so corresponding right eye positions could not be found LEFT EYE right ewe fixing UF FIGHT EYE Cleft ewe fixing OTA HAC em M Im DM AB 40 30 40 10 O 10 20 30 40 40 40 40 30 20 10 0 10 20 230 40 AB Horizontal Gaze deg longitude Estimating secondary changes takes
30. distinct though not mutually exclusive mechanisms to explain the observed path stability one mechanism supposed connective tissue to couple an anterior extent of each muscle to the globe the other supposed each muscle to pass through some sort of pulley coupled to the orbital wall Miller et al 1984 Miller et al 1990 Miller and Demer 1992 Simonsz personal communication has also emphasized the distinction between muscle paths per se and the path determining mechanism Normal Eye Conventional Model Pulley Model anatomic origin center of rotation gt aw Ota faa Mh Ps a Primary Position oe 14 Yo p E effective tangency B pulley location anatomic lt insertion axis of Tendon effectively stuck to Tendon slides through fascial pulley globe by intermuscuar membrane elastically coupled to orbital wall Orbit 1 0 was based on the first notion the conventional model Many strabismus syndromes were well simulated by Orbit 1 0 However simulations of muscle transposition surgery failed because Orbit 1 0 assumed that EOM bellies could sideslip in the orbit to follow transposed insertions Miller 1985 1999 09 04 A Biomechanical Approach 31 4 MRI study of muscle transposition We reasoned that under the conventional model muscle bellies would follow their transposed insertions whereas under a pulley model muscle bellies would remain near t
31. effect Summary Bibliography Clark RA M D Miller JM Ph D Demer JL M D Ph D 1998 Displacement of the Medial Rectus Pulley in Superior Oblique Palsy Investigative Ophthalmology and Visual Science vol 39 isu 1 pgs 207 212 PURPOSE The rectus extraocular muscles pass through fibromuscular connective tissue pulleys that stabilize muscle paths and control muscle pulling directions We investigated whether abnormal forces due to superior oblique SO palsy can displace pulleys and muscle paths METHODS Seven subjects were confirmed to have SO palsies by coronal MRI scans showing reduced SO cross sectional area and lack of contractile change with vertical gaze change Binocular misalignment was measured by Hess test In those 7 palsies and in 18 normal orbits coronal MRI scans corrected to standardized head position were analyzed to determine muscle paths in primary gaze Horizontal and vertical pulley coordinates known histologically to lie just posterior to the equator in primary gaze were inferred from these muscle paths RESULTS Normal pulley coordinates were very similar across normal orbits Compared with both normal and fellow orbits orbits with SO palsies showed a statistically significant 1 1 mm superior displacement of the medial rectus MR pulley No other pulley was significantly displaced from normal Computer simulation using the Orbit v 1 7 Eidactics Co biomechanical model of ocular statics showed
32. inflection points in the EOM paths from minimal posterior displacement to maximal anterior displacement should define the anteroposterior location of the EOM pulleys after transposition METHODS Contiguous cross sectional magnetic resonance images were obtained in planes perpendicular to the long axis of the orbit over its entire anteroposterior extent before and after operation in 6 patients who underwent rectus muscle transposition surgery Four patients underwent full tendon width transposition of the vertical rectus muscles laterally for lateral rectus palsy Two of these patients had augmentation of the transposition with sutures that fixated the temporal margins of the transposed muscles posteriorly to the sclera adjacent to the borders of the lateral rectus muscle One patient underwent full tendon width transposition of the horizontal rectus muscles superiorly for superior rectus palsy One patient underwent full tendon width transposition of both lateral rectus muscles inferiorly for A pattern esotropia Paths of EOMs were defined relative to the area centroid of the orbit Pulley locations were inferred from EOM paths The postoperative change in EOM pulley location was obtained by subtracting the preoperative pulley location from the postoperative pulley location for each image plane RESULTS For all patients the postoperative change in EOM belly location was relatively small posterior to the globe optic nerve junction The 2 patients
33. innervations to an eye moving passively or under cover given the position of the fixing eye and the parameters of both e Sherrington s Law of reciprocal innervation which relates innervations to paired antagonistic muscles Orbit does not include any models of central or peripheral adaptive processes or of post surgical healing However you can make hypotheses about these processes express them in Orbit s biomechanical parameters and derive their implications Similarly it cannot know the details of surgical technique eg how much tendon is lost in muscle recession but you can express your estimates in terms of Orbit parameters Robinson 1975 and Miller and Robinson 1984 describe the mathematical analysis on which Orbit is based This framework is fleshed out with data on 1999 09 04 18 Orbit 1 8 User s Manual extraocular geometry muscle paths muscle cross sections muscle forces and elasticities We use a description of normal orbital geometry derived from dissections of Volkmann 1869 serial sections by Nakagawa 1965 and MRI studies by Clark Clark et al 1997 Muscle paths and cross sections are derived from MRI studies of Miller Demer and colleagues Miller 1989 Miller et al 1993 Demer et al 1994 Demer and Miller 1995 Parameters and Variables We will use the term parameters or eye parameters to refer to values that characterize an eye and do not change as
34. of this simulation would be a treatment plan Many aspects of the model eye can be manipulated in pursuit of a diagnosis or treatment The Parameter Fitter described below partially automates the trial and error process Eye Position Coordinates for Translation The eye is cushioned in the orbit by elastic fat pads so it cannot only rotate it can also translate slightly For most purposes we can ignore globe translation but in some restrictive and co contractive syndromes globe translation is a significant factor as we will see when we analyze Duane s syndrome For now we just note that specifying translation is straightforward since we are all familiar with the conventional Cartesian coordinate system for describing translational motion Orbit uses Cartesian coordinates fixed to the skull with origin at the point where the center of the globe falls when the eye muscles exert no forces The three axes are oriented with a protrude retract axis aligned with the orbital axis an upward downward axis perpendicular to the first and as close to vertical as possible and a sideward middleward axis perpendicular to the other two The names used in Orbit to refer to these axes are the names of the positive directions sideward Positive sideward movement is translation toward the side of the head Sideward movement is not the same as conventionally defined lateral or temporal movement because our 1999 09 04 38
35. path from the muscle pulley the functional origin to point T The muscle pulls point T away from us with a total longitudinal force Fong which exerts a moment Mong The couple caused by the nonuniform distribution of force across the muscle s width see figure above results ina moment Mpigi Miotal Moone a MA iiti For a muscle of width w the angle subtended by the arc of tangency at the center of a globe of radius Rad is o W Rad The stress of an unbent muscle is s9 Fiong w and for the fiber at angle from the midpoint of the line of tangency S Sp LNG w where k is muscle stiffness and AL is the change in length of a fiber due to bending see Miller and Robinson 1984 1999 09 04 130 Orbit 1 8 User s Manual As shown in the right panel of the figure above we estimate the effect of sideways bending of the muscle with an angle B AL a B Rad The force s of each infinitesimal muscle fiber acts on a lever arm 7 producing a moment mM frxXs The total moment can be resolved into components due to longitudinal and width related forces we have op Mong Rad s Rad ot cos t Rad de 1 w ae op M pig Rad s KB Rad a sin a Rad da 2 w From 1 we have Ys Moone Rad s La Rad a cos a Rad da w h ha Rad fa cos a da 2 Rad s sin 78 sin 5 Vi Rad w 2 Rad 8 This moment is not a function of the bending angle B
36. simulation led to the discovery of soft rectus muscle pulleys As shown above the SR and IR pulleys hold the bellies of the transposed muscles near their pre surgical paths 1999 09 04 70 Orbit 1 8 User s Manual What happens without pulleys ES To eliminate pulleys from Orbit 1 8 thereby making it behave in this respect like Orbit 1 0 we locate RSR and RIR pulleys at the muscle origins in the left eye right eye and inner eye This requires the Expert User s Parameter Editor which shows coordinates of the muscle origins Without pulleys the transposed muscles take shortest paths which lie close to the RLR ME e ete TT TT DD Le Ce ih Te SH h P Baes eorr WAT Lr ani POT NT Pt a LHH TTT l rie ree ee Cy Ee Lt itt LALLIN renn y ani bl 1 Hl I Ifa I IMIT i wa hata DE AAT AAAA AA ea aa B TEELEN EI en J A eS i J T E knr oie 5 eT al een AN E e E a a Seno Tesna Such muscle paths are not observed in post operative magnetic resonance images Miller et al 1993 The resulting simulated alignment is both alarming and unphysiologic RLR Palsy PstOp sim no puleys LEFT EYE right eye fixing UP FIGHT EYE Cleft ewe fixing OTA HAN ea ao 30 40 10 O 10 20 30 40 40 al 40 40 s30 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude The significant difference between the simulations with and without pulleys is the strangely varying horizontal misali
37. some thought and some guesswork since we have only begun to characterize strabismus syndromes in biomechanical terms and to develop ways to estimate parameters in individual patients Demer and Kerman 1994 Demer et al 1994 Demer et al 1995 Demer and Miller 1997 Demer et al 1998 Demer et al 1999 Demer and Miller 1999 e We expect atrophy of a chronically paralyzed muscle marked reductions in cross section have been measured by MRI Demer and Miller 1995 Let s 1999 09 04 Tutorial 6 estimate a 50 reduction in RLR Elastic Muscle Strength e Undoubtedly the RLR will stretch We estimate 2 mm of stretch supposing that the muscle adapts to the eye s chronic esotropia e There is evidence that modest atrophy occurs in the antagonist of a paralyzed muscle We model this by reducing RMR Contractile Muscle Strength and RMR Elastic Muscle Strength both to 70 of normal e The RMR too should adapt to its chronically reduced path length We estimate it shortens 2 mm e Finally we know that the antagonist of a chronically paralyzed muscle may become fibrotic resisting elongation beyond what is due to its slight shortening This is easily simulated by increasing RMR Stretch Sensitivity to 125 see the section Manipulating the Muscle Model above 3 Using the Right Eye Parameter Editor make these secondary changes Contractile Muscle Strength of normal Po C 100 C 100 C
38. than we do here We would say instead that a short muscle must be stretched more than a long muscle to cover the same path and so exerts more elastic force Orbit can also be used to simulate and test your hypotheses about changes in muscle cross section eg hypertrophy or atrophy or tissue properties eg fibrosis which may occur over time in a resected muscle or its antagonist Such secondary changes cannot be calculated automatically however because they are not so far as we know necessary consequences of resection and in any case little is known about their determinants Orbit simulation is currently the only practical way to test such clinical and scientific hypotheses Contractile Force strong vs weak Contractile force depends mostly on innervation which causes each sarcomere one of the serial contractile elements of a muscle fiber to shorten There is also a length dependency intrinsic to the sarcomeres they have an optimal length for force generation Stretched or crushed sarcomeres develop less force at given innervations The contractile force model built into Orbit automatically reflects these effects Orbit also provides parameters with which you can alter each muscle s response to a given level of innervation Orbit does not for reasons that should now be clear automatically calculate central innervational adaptations that might follow from strabismic lesions or muscle manipulations This ma
39. the initial values for the fitting algorithm This may be useful if since initially dragging parameters to the Parameter Fitter the simulation has been updated eg by previously Applying fitted values _Apply_ places the fitted values into the simulation It can be used when the fitting procedure finishes or when it is stopped with 1999 09 04 Orbit Reference 101 A multidimensional fitting routine is not guaranteed to work in every case Some tips e Be sure the Fitter can get started If Initial Error is 9999 99 one or more gaze positions cannot be solved for the initial parameters Change an initial parameter or look at the Alignment Viewer to find the gazes at fault Then either allow for that number of Convergence Failures or remove the troublesome positions with the Intended Gaze Editor e It will usually improve the fit to re run the Fitter after it claims to have found a minimum Thus after fitting you might click Apply Load Initial and Fit to start a new search from the previously found parameters e You must always ask yourself Do these parameter values make sense To fit n parameters the Nelder Mead Simplex algorithm works in an n dimensional space with n 1 points eg a triangle for n 2 a simplex in general which might contain the sought for minimum On each iteration it varies one or more parameters to learn about the local terrain and when it has varied all parameters guess
40. the new calculation infinitesimal moments are summed across the width of the muscle The resulting total moment is then resolved into a moment tangential to the globe the pure pulling effect of the muscle applied to the center of the line of tangency and a moment normal to the globe the twisting effect of the nonuniform force distribution across the muscle In Orbit s terms rotational muscle force the total moment produced by a muscle on the globe is the sum of two moments 1 the rotational force due to longitudinal muscle force which is the result of total longitudinal muscle force acting on the arm joining the center of rotation with the point of tangency of the muscle centerline with the globe and 2 the rotational force due to muscle width which is the result of the couple pair of forces due to force distribution across the muscle width acting about the axis joining the center of rotation with the point of tangency rotational muscle rotational force moment to a force a total moment force total longitudinal muscle force rotational force moment due to muscle width 1999 09 04 Math 129 arc of tangency The figure below left shows a section of the globe containing the arc of tangency of the wide muscle with the globe The midpoint of the arc of tangency is T The plane of this arc contains the globe center C and is perpendicular to the muscle
41. their dynamic role in ocular motility Clark RA Miller JM Demer JL 1997 Location and stability of rectus muscle pulleys inferred from muscle paths Invest Ophthalmol Vis Sct vol 38 pgs 227 240 PURPOSE The paths of rectus extraocular muscles EOMs are constrained by pulleys connective tissue sleeves mechanically coupled to the orbital walls This study investigated using high resolution magnetic resonance imaging MRI the location and stability of EOM pulleys in normal and strabismic subjects METHODS Multiple contiguous coronal MRI scans spanning the anteroposterior extent of the orbit during primary gaze upgaze downgaze adduction and abduction were digitally analyzed to 1999 09 04 Annotated Orbit Bibliography 141 determine paths of rectus EOMs Pulley locations were inferred from EOM paths RESULTS Data for ten orbits of six normal subjects established normal paths of rectus EOMs in primary gaze Muscle paths in primary position were highly uniform across normal subjects In secondary gaze positions EOM paths at the level of the pulleys exhibited small but consistent shifts relative to the orbit opposite the direction of gaze consistent with expected mechanical effects of intermuscular connective tissue suspensions of the pulleys Twelve orbits of seven strabismic subjects showed as a group no significant difference from normal in EOM paths in primary gaze and no significant difference from norm
42. this folder we have provided alignment measurements that are the mean of measurements we collected from 3 cases of left superior oblique palsy confirmed by MRI Demer et al 1995 o and with similar surgical treatment L50 Palsy Prep LE meas ke E and s0 Palsy Prep RE meas We will refer to such data as clinical alignment measurements alignment measurements or just measurements the important distinction being between measurements and simulations Simulations can predict measurements and measurements can test simulations but they are not the same Orbit measurement files are plain text files like those that can be produced by text processor and spreadsheet programs these programs must usually be set to output plain text Orbit can also save measurements and simulated positions as text files Details are given in the Orbit Reference section below 1999 09 04 Orbit 1 8 User s Manual tS To import pre operative measurements into Orbit s left eye select Left Eye Import Measurements which will lead to a standard Macintosh File Dialog we show the new file dialogs supported by Apple Navigation Services incorporated in MacOS 8 5 if you are using an older operating system you may see the older style file dialogs instead Navigate to the LSO Palsy Example folder Lai LSO Palsy Example Date Modified Tr T L50 Palsy Fre p LE meas 1999 04 06 LSU Palsy Prep RE meas 1399 04 06
43. to introduce comment lines tabs and spaces at the beginning of a line allowing indentation and all characters that are not digits or so numbers must not be expressed in scientific or engineering notation Recall that excyclorotation as in field 5 is abnormal extorsion extorsion beyond that expected from Listing s Law For eyes that obey Listing s Law eg normal eyes excyclorotation will always be zero 1999 09 04 104 Orbit 1 8 User s Manual Here is an example of a valid import file Generic LR Palsy PreOp measurements for Orbit 1 8 tutorial Intended Following Eye Up Ab Up Excy 237 14 O 37 O 15 38 13 30 22r 20 a15 26 14 O 29 O 15 26 13 30 26 21 30 o 15 O 14 28 16 O 14 28 17 15 O O O O O O O O O O O O O O O O O O O O O 1999 09 04 Orbit Reference 105 Exporting Measurements amp Simulated positions If you have imported clinical measurements or entered or modified clinical measurements using the Measured Gaze Editor you may want to write them to a text file for use with another application such as a text editor or spreadsheet To write measurements to a file use Left Eye Export Measurements Or Right Eye Export Measurements It may also be useful to write simulated gaze positions to a text file Use Left Eye Export Simulation or Right Eye Export Simulation Orbit
44. with abducens palsy who underwent placement of posterior augmentation sutures however demonstrated a significantly larger displacement of the posterior vertical rectus paths compared with similar patients who did not receive augmentation sutures For all horizontally transposed vertical rectus muscles and inferiorly transposed lateral rectus muscles the inflection of the EOM path began 3 mm anterior to the elobe optic nerve junction For the superiorly transposed medial rectus muscle and lateral rectus muscle the inflection began 6 mm anterior to the globe optic nerve junction CONCLUSIONS The anteroposterior locations of the EOM pulleys can be defined by analysis of EOM displacement after transposition surgery Augmentation of transpositions by posterior suturing displaces the EOM pulleys substantially more than non augmented transpositions 1999 09 04 Annotated Orbit Bibliography 139 Demer JL Miller JM 1999 Orbital Imaging in Strabismus Surgery In eds Rosenbaum A and Santiago AP Clinical Strabismus Management cty Philadelphia pub W B Saunders Introduction History of orbital imaging Principles and techniques General principles of orbital imaging Technique of orbital magnetic resonance imaging MRI Technique of orbital CT Functional anatomy of normal extraocular muscles Some clinical applications Extraocular muscle paralysis Extraocular muscle heterotopy Severed and extirpated muscles Entrapment Mass
45. 10 mm rubber band resting length 10 mm and extending it by 10 mm path length 20 mm fractional stretch 20 10 10 100 Then cut off half of the band resting length 5 mm and again extend it by 10 mm stretch 15 5 5 200 It s harder to hold extended now because fractional stretch is higher Each unit length of the band is now stretched to 3 times its resting length compared to 2 times before it was cut Cutting a piece off the band did not change its intrinsic properties the band is still made of the same rubber material and has the same cross section Similarly the intrinsic stiffness of a muscle is determined by the nature of the elastic properties of the tissue eg its fibrous content and its cross section and is measured in grams fractional stretch Cutting off a piece of 1999 09 04 A Biomechanical Approach 21 muscle changing its resting length only changes the fractional stretch of the muscle eg from 100 to 200 for a given absolute movement of its end eg 10 mm thereby changing its elastic force We describe elastic muscle stiffness in terms of fractional or percent change in length because then stiffness is an independent parameter not dependent on resting muscle length If we instead defined muscle stiffness in terms of absolute stretch mm it would change with resection So when one says a short muscle is stiff one is using a different meaning of stiffness
46. 100 L 100 Elastic Muscle Strength of normal Stretch Sensitivity 3 of normal Relaxed Muscle Length mm without tendon Note the unusual normal value of 150 for IO Stretch Sensitivity is an interim solution to the problem of not yet knowing how to model the IO with Lockwood s Ligament With the usual 100 value the IO exerts too little elastic force in downgaze 1999 09 04 68 Orbit 1 8 User s Manual 5 Then activate the Alignment Viewer RLR Palsy PreOp sim 2 LEFT EYE right eye fixing UP FIGHT EYE Cleft ewe fixing OTA WA ea ao AB 40 SO 20 10 10 20 30 40 40 a 4O0 40 s0 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude The right eye shows a typical esotropic pattern with abduction not reaching the midline Part of the left eye pattern is missing because of the paretic right eye s restricted range of fixation Note however that the left eye measurements are more complete than the left eye simulation This probably indicates a problem with the clinical measurements Consider where the left eye intends to fix primary position filled red dot in left panel above This measurement should be the position of the following left eye where the right eye fixes primary position But from the right eye positions in the right panel it appears that the right eye cannot get to primary position If by extreme effort the patient did get his right eye to primary position then
47. 564 4 Oy ee If you received Orbit over Internet you will instead have a single archive file Orbit 1 8 s36 CS In either case double click Orbit 1 8 sea to unpack the archive and get the Orbit 1 8 f folder tS If you received Orbit on a CD ROM simply drag the Orbit 1 8 f folder from the CD ROM to your hard disk 1999 09 04 Preliminaries 9 Orbit Installation Files tS Open the folder and you should see something like this i Orbit 1 8 f 10 items 3 2 GB available Orbit 1 3 User Manual Orbit 1 6 Orbit 1 3 Release Notes me f ji an Es tr Orbit Mor m Orbit Po Orbit_Prefs 2 LSO Palsy Example RLA Palsy Example Duane Syndrome Examples For System 6 0 amp 3 1 Only is the Orbit program application in Macintosh parlance To run launch Orbit you can double click orbit 1 8 this icon drop a simulation file on it etc Whenever you launch an unregistered copy of Orbit you have the option of entering registration information or running in demonstration demo mode Orbit operates normally in demo mode except that output functions saving exporting and printing are disabled r This copy of Orbit is currently unregistered and Cc s0 will function as a Demonstration Yersion you will not be able to save or print your work Enter your Registration Information below and click Register or click Demo License Humber
48. A dloo isfoo Norm 19971015 Chart type lancaster fick rel Hone UF FIGHT EYE left eye fixing Primary Position Ht207 4307 V30 430 1 e Soe ee ee eee ee ee ee ee I lJ H 30 41 5 V430 At a nic 30 Ht40 420 W400 420 o t gt 0 H409 420 Wd 4207 ne co a ai 10 Ht40 410 Wt20 410 cal S E H407 45 Yeo cat H 0 V409 45 5 10 H40 45 YEO amp HO wigo a5 q 20 30 F 40 Experienced and Expert Users can choose gaze patterns not available in the Set Pattern popup list by opening Both Eyes Gaze Selector untitled Enara Set Pattern A intended Gaze Selector Set Pattern i AE Left Eye Intended Gaze Angles 7 AD x AD a Eye Intended Gaze Angles 7 AB gt POBEVEESEOEOEBV9O9 TATE GISEE046C000000000 ttt eee eee ee tet z G OQ QO O 36 SISI amp G 5 Q e ei OC GG r G 50 Q O O Q O Or OG 3 Or OO GO OC er 00000000006000000 00000000000000000 r QGOQ aa LELELE PIELE QQ Lele eree ele GOGO a a GQQ Q JG P 2 Lf P OOOOOORO HT DE 1 s i O og The main part of the window consists of two panels containing buttons click on these buttons to choose the 1999 09 04 Orbit Reference 91 gaze angles to which each simulated eye attempts to rotate moving under cover Intended gaze positions of the left eye are chosen on the
49. Annotated Orbit Bibliography 149 Spin Offs Dennerlein JT Miller JM Mote Jr CD Rempel DM 1997 A low profile human tendon force transducer The influence of tendon thickness on calibration Journal of Biomechanics vol 30 isu 4 pgs 395 397 An in vitro calibration method for human tendon force transducers using tendon thickness to predict the calibration factor has been previously proposed An et al J Biomechanics 23 12 1990 However changes in the calibration factor due to changing tendon geometry during repeated tendon loading are unknown A low profile transducer design that measures tendon thickness in the transducer in situ is developed An empirical model estimating the transducer s calibration factor is developed using data from in vitro tension testing of 12 fresh frozen human finger flexor tendons Each tendon is pre seated with ten loading cycles before data collection Using tendon thickness the model predicts the measured calibration factor within 0 to 15 average 6 During repeated loading of an in vitro tendon the calibration factor changes 15 over the first ten cycles 0 to 50 N due to the observed changing tendon thickness After these first ten loading cycles the variability of the calibration factor is reduced to less than 1 for the next three loading cycles Hence this new in vitro calibration procedures with tendon pre seating reduces the cycle to cycle variability caused by the associate
50. Internally the two values are simply multiplied so eg doubling either has the same effect The values of muscle forces and the rotational stiffness of non muscular orbital tissues are derived from intraoperative and other measurements of Collins et al 1975 1981 Translational stiffness of the globe important in simulating restrictive and co contractive syndromes is estimated from the data of Dyer and Henderson 1958 Hering s Law of Equal Innervation is simulated by converting innervation sets of the fixing eye into equivalent with respect to a normal eye gaze angles reflecting the gaze angles across the midline and converting back into innervation sets This procedure is schematized in the Test of Binocular Alignment section below Sherrington s Law of Reciprocal Innervation is hard coded as described by Robinson 1975 It may be possible in a future version of Orbit to solve for each of the 6 innervations in a set independently thereby simulating rather than assuming the exact form of reciprocal innervation 1999 09 04 26 Orbit 1 8 User s Manual Basic Data and Operations Orbit operates on three types of data innervations gaze positions and eye parameters solving a force balance equation to determine innervations from positions and parameters or positions from innervations and parameters These two types of solutions answer two types of questions 1 What innervation set is required t
51. Louis pub Mosby Whitnall 1932 Anatomy of the Human Orbit edn 2 cty London pub Oxford Medical Publications Williams PE Goldspink G 1973 The effect of immobilization on the longitudinal growth of striated muscle fibers Journal of Anatomy vol 116 pgs 45 55 Williams PE Goldspink G 1978 Changes in sarcomere length and physiological properties in immobilized muscle Journal of Anatomy vol 127 pgs 459 468 1999 09 04 154 Orbit 1 8 User s Manual 1999 09 04 Order Form amp License Agreement 155 Eidactics Visual Biosimulation FEIN 94 3185295 Suite 404 1450 Greenwich St San Francisco CA 94109 1466 vox amp fax 415 921 8678 email sales eidactics com web www eidactics com ePlease issue Orbit Gaze Mechanics Simulation licenses 750 e am already licensed Send __ upgrades to the current version 100 With each Orbit license or upgrade you will receive a printed User s Manual and a CD ROM containing the Orbit application Orbit User s Manual tutorial files and several Orbit QuickTime movies demonstrating normal and strabismic eye alignment The below designated licensee will receive a registration key used to enable the full features of Orbit the later obtained from our CD ROM or Web site Orbit software that has not been enabled by entering a license code is demonstration software Orbit Demo and may be freely distributed as specified in the
52. Registration Key OO O O Call upper case letters 1999 09 04 10 Orbit 1 8 User s Manual POF If you have purchased an Orbit license see the Order Form amp License Agreement near the back of this Manual you will have received a card containing your registration information Orbit 1 8 Gaze Mechanics Simulation Below is your Orbit registration information Enter it when you launch an unregistered copy of Orbit Remember the User named below is responsible for assuring that only one copy with this License Number is in use at any time User Name Joel M Miller PhD Institution Eidactics i License Humber 490 Registration Key Call upper case letters ed Enter all four lines as shown on the card The registration key is always exactly 10 upper case English letters If you misplace your registration information we can provide it from our files is a description of improvements in and limitations of the new version Adobe Acrobat Drbit 1 4 Release Notes Reader 3 or better provided on CD ROM and pi Orbit_Nerrn available free from Adobe at www adobe com is needed to read it The following 3 files are used by Orbit Most users will not deal with them directly Be sure to keep them together with Orbit in the same folder is the standard set of normal eye parameters used by Orbit When Orbit is launched Orbit_Norm is read in as the description of norm
53. SO palsies established norms for morphology and contractility On SO contraction in down gaze maximum cross sectional area was significantly P lt 0 001 greater than on relaxation in up gaze and the point of maximum cross section shifted posteriorly with contraction In seven subjects with clinically unilateral chronic SO palsies the affected muscle was significantly smaller than normal P lt 0 001 and lacked contractile changes clinically normal fellow SO muscles exhibited normal cross sections and contractile changes CONCLUSION High resolution MRI coupled with quantitative morphometric analysis can demonstrate the size and contractility of the normal SO muscle The technique which can be employed using widely available clinical equipment is also sensitive enough to detect anatomic and functional changes expected in chronic SO palsies Miller JM Demer JL Rosenbaum AL 1993 Effect of transposition surgery on rectus muscle paths by magnetic resonance imaging Ophthalmology vol 100 isu 4 pgs 475 87 PURPOSE To evaluate effects of transposition on extraocular rectus muscle paths in middle and deep orbit METHODS The effect of various transposition procedures was assessed in five patients using surface coil magnetic resonance imaging MRI performed with controlled gaze before and after surgery Path changes were compared with those expected under conventional concepts of functional orbital anatomy quantified by biome
54. Set Beep when done to be alerted when a fit is achieved Click to accept the settings shown for the current simulation and return to the Parameter Fitter _Canee1 to abandon any changes and return or to make the window show the values from Preferences The Fit button starts the parameter fitting algorithm The wait cursor will show that Orbit is busy As the fitter works it will show Iteration the number of parameter sets tried Initial Mean Error or Initial Maximum Error the fitting error for the initial parameter values A special error value of 9999 99 means that with the initial parameters solutions could not be found at more points than allowed by the Convergence Failures Allowed setting Either pick better initial parameter values or allow more convergence failures Current Mean Error Or Current Maximum Error the fitting error for the current parameter values This field updates as the algorithm works The 9999 99 error value meaning excessive convergence failures is normal during fitting the procedure will back away from the troublesome parameter value and try something else Watch the Iteration Current Error and Fit value fields to judge the algorithm s progress If it seems to be going wrong unbelievable parameter values or nowhere stuck in a local minimum hold down both the and keys until the algorithm stops takes corresponding values from the simulation and makes them
55. TS Pulley structure were located within posterior Tenon s fascia closely surrounding the medial rectus muscle Pulleys were comprised of a dense collagen matrix with alternating bands of collagen fibers precisely arranged at right angles to one another This three dimensional organization most likely confers high tensile strength to the pulley Elastin fibrils were interspersed in the collagen matrix Fibroblasts and mast cells were scattered throughout the relatively acellular and avascular collagen latticework Connective tissue and smooth muscle bundles suspended the pulley from the periorbita Smooth muscle was distributed in small discrete bundles attached deeply into the dense pulley tissue CONCLUSIONS Fine structural observations confirm the existence and substantial structure of a pulley system in association with the medial rectus extraocular muscle The presence of pulleys must be considered in models of the oculomotor plant The cytoarchitecture and placement of pulleys suggest that they are internally rigid 1999 09 04 142 Orbit 1 8 User s Manual structures and are consistent with the idea that they determine functional origins for the extraocular muscles However the nature of the connective tissue smooth muscle struts suspending the pulley system to the orbit supports the notion that the pulley position and thus the vector force of the eye muscles may be adjustable Demer JL Miller JM Poukens V Vint
56. a function of eye position A muscle s origin stiffness and resting length are all eye parameters All other Orbit values which can vary as a function of eye position are vartables Elastic muscle force and muscle path length are examples of variables Note eg that stiffness change in force fractional change in length is an independent intrinsic muscle property that is a parameter whereas elastic force a variable depends on stiffness muscle resting length and muscle path length The length of the path over which a muscle travels depends on the shape of the path which depends on eye position total muscle force and pulley stiffness among other things Fixing and Following Eyes We use eye alignment and binocular alignment to refer to phoria not tropia This follows from the fact that Orbit treats biomechanical factors only and knows nothing about such sensory factors as fusional range Thus when we talk about alignment you should imagine some test of eye alignment that completely dissociates the two eyes in the sense of providing no binocular visual alignment cues It is essential to know which eye is the fixing eye the eye voluntarily turned by the subject to point in a known direction and which eye is the following eye the eye which is moving under the influence of innervations determined by the fixing eye passively or under cover The Hess and Lancaster tests approximate this ideal situation
57. al eyes When a new simulation is created parameters from Orbit_Norm are 1999 09 04 Preliminaries 11 S Orbit_Prets a Orbit POY stored as starting values in the new document Factory Settings for all Preferences are also stored in this file this allows you to return to these standard settings whenever you wish It is possible for knowledgeable users to modify Orbit_Norm it is a plain text file to incorporate new data about normal eye mechanics or create versions for different ages races sexes and species If you do this be careful to only change values of existing parameters or add comment lines If you alter Orbit_Norm or replace it with a new version remember that only newly created simulations will reflect the change Existing simulations that are opened or modified will not Orbit will complain when it is launched if it does not find Orbit_Norm in its folder stores your Preferences for New Simulations that is the settings you make as explained below to customize the way Orbit creates new simulations it initially stores standard Factory Settings You can create different sets of preferences for different users simply swap the desired Orbit_Prefs into Orbit s folder If there is no Orbit_Prefs file in its folder Orbit will create one with Factory Settings Orbit_Prefs also stores your registration information If you wish to give a copy of Orbit to a colleague give him or he
58. al in changes of paths of EOMs in secondary gaze positions Two subjects with incomitant strabismus were found to have grossly abnormal EOM paths in primary gaze suggesting heterotopic pulleys Computer simulations of these heterotopic pulley locations accounted for the observed patterns of incomitant strabismus in both cases CONCLUSION High resolution MRI can determine the location and compliance of rectus EOM pulleys Pulley position is highly uniform across normal subjects consistent with the notion that musculo orbital pulleys determine pulling directions of rectus EOMs In both normal and strabismic subjects pulleys exhibit small shifts with eccentric gaze that are consistent with secondary intermuscular but not musculo global mechanical couplings Heterotopic pulley position is a potential cause of incomitant strabismus Porter JD Poukens V Baker RS Demer JL 1996 Structure function correlations in the human medial rectus extraocular muscle pulleys Invest Ophthalmol Vis Sci vol 37 isu 2 pgs 468 72 PURPOSE Fibroelastic pulleys function like the trochlea to fix the position and pulling direction of the recti extraocular muscles within the orbit This study characterized the fine structure of the human medial rectus muscle pulley METHODS Human medial rectus muscle pulley tissue was dissected at autopsy immersed in aldehyde fixative solution and processed for and examined with light and electron microscopy RESUL
59. anical factors have made analysis far from the straightforward exercise it once seemed Some workers have found such efforts of little interest believing that non mechanical factors were of overwhelming importance or that variation across patients and surgical techniques would make any general analysis useless in individual cases Some are uncomfortable treating a familiar discipline in unfamiliar terms We review efforts to construct a useful biomechanical model of binocular alignment and the physiologic studies of muscle paths and forces engineering developments muscle force measurements and computer software and clinical research model testing and application spawned by modeling efforts Although general clinical utility lies in the future these models are already useful in special cases in which complexity frustrates mental calculations or in which surgeons have no relevant experience egs grossly abnormal orbits prosthetic muscles We describe how some differences among subjects may be directly measured and how remaining differences can be estimated by adaptive models Given a correct mechanical model non mechanical factors will be more easily isolated and studied Finally we describe a graphical computer program a software ophthalmotrope which provides intuitive access to biomechanical strabismus models 1999 09 04 136 Orbit 1 8 User s Manual Biomechanical Models of Eye Alignment Miller JM Pav
60. as expected If manipulations are confined to one muscle or tendon it is easier to find the correct parameter with Live Eyes On the other hand if you re working with several muscles the Parameter Editor will be more convenient The Live Eyes have 26 regions that produce pop up windows when you click them These regions are the 12 tendons the 12 muscles and the 2 globes A desired region can be made visible by changing Point of View or by using the windows settings button WAE to hide occluding structures In simulating resection surgery you may reduce a Live Eyes tendon length to zero and then be surprised to find that a length of tendon is still shown This is intentional since if a tendon disappeared its pop up window would become inaccessible Show heise f Lso hirso V RSR hete bef lGib bef LAR hei RR bef Rob bef ELR heie efon rio ef RIR Clicking the windows settings button Wik allows you to choose which structures are shown You can adopt previously set simulation preferences as current window settings with Apply your choices to the current Live Eyes window by clicking Lok or forget them by clicking Cancel J 1999 09 04 96 Orbit 1 8 User s Manual Live Eyes are drawn with Left Eye and Right Eye parameters driven by Normal primary position innervations This allows the Live Eyes to be drawn regardless of parameter values Consequently the Live Eye will now show abnor
61. but still ran out of memory open Orbit Info and increase Preferred size Close the box and try Orbit again 4 If your basic problem is insufficient installed memory you should have at least 8 MB available to Orbit buy more If you have a lot of free disk space an easy but unattractive solution Orbit will run slowly is to turn on or increase the size of Virtual Memory Consult your Macintosh User s Guide 1999 09 04 12 Orbit 1 8 User s Manual Frequently Asked Questions There will be many questions from Users about how Orbit works how to use it and how to cast clinical entities into its terms We begin a FAQ section here and update it in subsequent editions of this manual Between editions a current FAQ list will be maintained on our website at www eidactics com How do the various Preferences and Window Settings differ The basic difference is the scope or range over which the settings are effective Preferences for New Simulations only affect simulations subsequently created with File New Existing simulations whether currently open or not are unaffected Preferences for New Simulations are stored in the special file Orbit_Prefs which must be in the same folder as the Orbit application Preferences for Sim where is the name of the active simulation apply to the active simulation only When the active simulation is closed these preferences are saved in the simu
62. chanical modeling RESULTS Vertical rectus transpositions of 6 to 10 mm produced changes in muscle paths of 3 mm or less assessed posterior to the equator of the globe Lateral rectus transpositions as large as 10 mm resulted in almost no movement of muscle bellies Conventional modeling predicted much larger changes CONCLUSION The authors observed less movement of rectus muscle bellies relative to orbital walls than would be expected under the traditional assumption that transposed muscles follow the shortest path from origin to insertion This implies that middle and deep orbital tissues connective tissues and compartmentalized orbital fat constrain the paths of rectus muscle bellies preventing them from sliding freely to follow their transposed insertions The authors propose that these tissues function as pulleys elastically coupled to the orbital wall and that they are important determinants of extraocular muscle function Miller JM Robins D 1992 Extraocular muscle forces in alert monkey Vision Res vol 32 isu 6 pgs 1099 113 We describe an extraocular muscle EOM force transducer that provides low noise signals from an alert animal for several months is implanted without disinserting the muscle and is well tolerated by the body and present results obtained with the device The transducer can be used to study orbital statics and dynamics and oculomotor control signals undiminished by orbital low pass filtering
63. click _8K_ Existing and new Live Eyes and Graphic Eyes will be shown from the new POV 1999 09 04 Orbit Reference 113 Graphic Eyes Graphic Eyes produces a high resolution picture of following and fixing eyes in any of the gaze positions previously selected with the Intended Gaze Selector the Live Eyes display shows only primary position its main purpose being access to eye parameters Muscles are shown in red with saturation related to one of several model variables Select Left Eye Graphic Eyes for a representation in which the left eye is following and the right eye fixing or Right Eye Graphic Eyes for the reverse The window settings button ii provides the following options Show kise fso Virso yf esr MY LLE fe Lab bef LAR RMR bef Rob bef ELR heie efo rio bef RIR Muscle Color Minimum Saturation ol Variable Total Muscle Force Maximum Saturation Files L Beautify _ write FICTs Choose Folder The two groups of 7 check boxes let you chose which structures are shown Below them is a popup list of variables than can be represented by muscle color Choose total muscle force in grams contractile muscle force in grams elastic muscle force in grams stretch in mm relative to relaxed length stretch as percent change from relaxed length or innervation in arbitrary units Then set the values to be associated with minimum gray and ma
64. d change in the tendon thickness Pfann KD Keller EL Miller JM 1995 New models of the oculomotor mechanics based on data obtained with chronic muscle force transducers Ann Biomed Eng vol 23 isu 4 pgs 346 58 Several phenomenological models of the oculomotor mechanics that produce saccadic eye movements have been developed These models have been based on measurements of macroscopic muscle and orbital tissue properties and measurements of eye kinematics during saccades We recorded the forces generated by the medial and lateral recti during saccades in an alert behaving monkey using chronically implanted force transducers With this new data we tested the ability of the classic saccade models to generate realistic muscle force profiles Errors in the predictions of the classic saccade models led to a reexamination of the current models of extraocular muscle Both a phenomenological Hill type muscle model and an approximation to Huxley s molecular level muscle model based on the cross bridge mechanism of contraction distribution moment model were derived and studied for monkey extraocular muscle Simulations of the distribution moment model led to insights suggesting i specific modifications in the lumped force velocity relationship in the Hill type model that resulted in this type of phenomenological model being able to generate realistic dynamics in extraocular muscle during saccades ii the distribution of activity in the diff
65. demo cannot export measurements or simulated gaze positions intended abduction deg intended elevation deg measured or simulated abduction deg measured or simulated elevation deg measured or simulated excyclorotation deg measured or simulated sideways globe translation measured Simulated protruding globe translation measured Simulated upward globe translation mm measured Simulated extorsion deg Export formats are similar to import formats see above with the addition of a 9th field on each line Measured or simulated extorsion is included for the convenience of workers who need the 3rd Fick coordinate of measured or simulated gaze You will recall that Field 5 excyclorotation is not the torsion value that goes with abduction and elevation it is abnormal torsion Thus excyclorotation extorsion normal_extorsion where normal_extorsion follows Listing s Law Clinicians we think will usually be interested in excyclorotation and scientists in extorsion 1999 09 04 106 Orbit 1 8 User s Manual Mechanical State Viewer The Mechanical State Viewer shows rotations deviations innervations forces and other variables determined by simulation for a given gaze position In contrast the Parameter Editor is used to view and edit parameters values that characterize an eye and are constant across gaze positions The title bar of the Mechanical State Viewer shows the simulation na
66. e reflect the position Fixable Now we can find the 3 Position reciprocally related across the innervation pairs that midline and 5 would drive the Fixing transform back La Set Eye to the Fixable into Position innervation C space The eee But the 2 eyes are Inner Eye is mirror images eg simply a third Find when the fixing eye set of eye Sela abducts the following parameters eye adducts so to get that is sisually Following Eye eft with the ae lig ory Geese tye mento may be Midline across the midline modified Intended Position gt Both Eyes Inner Eye Parameter Editor Find Parameters secre Finally D i this Innervation SE Set to Following MAA D iaa dreas Eye and a 7 description of Following Eye Find agai E me the following pasion aan a eye go to Find Boston which ee calculates the position of the following eye 1999 09 04 A Biomechanical Approach 37 If the fixing eye is normal only the calculations in box E are necessary this was the total calculation in Orbit 1 0 We can compare such a set of simulated gaze positions with a set of clinical measurements altering eye parameters to optimize the fit The outcome of such a simulation is a diagnosis of the patient s disorder in biomechanical terms Similarly we can find the orbital manipulations that would cause our model sick eye to assume normal conjugate gaze positions The outcome
67. e human orbit contains specialized musculofibroelastic tissues in and just posterior to Tenon s fascia which serve as pulleys determining actions of recti extraocular muscles Unimpaired pulley function is essential to effective muscle transposition surgery Scott AB Miller JM Collins CC 1992 Eye muscle prosthesis J Pediatr Ophthalmol Strabismus vol 29 isu 4 pgs 216 8 We inserted a silicone rubber elastic band along the course of a paralyzed lateral rectus and of a paralyzed superior oblique to restore alignment and to provide a spring against which the antagonist could 1999 09 04 148 Orbit 1 8 User s Manual pull The lateral rectus band has been in place for 7 years It provides alignment and a field of single binocular vision of 20 degrees The superior oblique band has been in place for 17 months It provides alignment and single vision over 30 degrees from the primary position except for a restriction in upgaze adduction to 25 degrees Brown syndrome and in downgaze adduction to 20 degrees Such engineered elastic bands are a useful addition to current surgical techniques for management of cases of paralysis and restriction Miller JM Demer JL et al 1990 Two mechanisms of up shoots and down shoots in Duane s syndrome revealed by a new magnetic resonance imaging MRI technique In Campos EC ed Strabismus and Ocular Motility Disorders London Macmillian Press pgs 229 234 1999 09 04
68. e system and take primary position straight ahead as 0 0 O The reasons are partly historical in that Robinson 1975 used Fick coordinates and partly practical because clinicians speaking about horizontal and vertical eye movement are usually it seems thinking of a longitude latitude system Note that horizontal and vertical are not well defined unless a coordinate system is specified In connection with Orbit simulations horizontal rotation will always mean a change in longitude only and vertical rotation will always mean a change in latitude only according to the Fick coordinate system The term gaze is conventionally used to refer to the direction of the visual axis only that is to horizontal and vertical components leaving torsion unspecified Thus we specify intended gaze in Orbit simulations and fixing eye gaze in clinical eye alignment tests because patients are not asked to bring the fixing eye toa specified torsional position and indeed without special training Nakayama and Balliet 1977 they cannot 1999 09 04 A Biomechanical Approach 4 Finally we have chosen coordinate directions that take advantage of the mirror symmetry of the eyes eg we use abduction adduction instead of rightward leftward This allows us to describe gaze mechanics in a way that is valid for either eye We use coordinate names that indicate which direction is positive abd
69. ear 1999 09 04 84 Orbit 1 8 User s Manual Preferences There are three types of settings with which you can customize the behavior and appearance of Orbit and simulations you create They differ in scope e Preferences for New Simulations can be set to customize subsequently created new simulations These preferences are saved in the file Orbit_Prefs which is associated with the Orbit application Thus these preferences remain in effect for a given copy of Orbit until you change them or trash the Orbit_Prefs file e Preferences for Active Sim sim_name contains many of the same settings but only affects the currently active simulation These preferences are saved are saved in the simulation file and so re assert themselves only when that simulation is opened e Finally several windows offer Window Settings buttons Wii which can be used to quickly and temporarily override the preferences for that window only These are described in connection with individual windows The Preferences window Both Eyes Preferences for New Simulations lets you to customize simulations that you subsequently create using File New The Preferences window Both Eyes Preferences for Active Sim sim_name lets you customize the simulation that is currently active The contents of the two preferences windows are similar EEEE Offers this explanatory page Returns all preferences to factory settings
70. eby allowing the remaining serial sarcomeres to operate at their optimal lengths Tabary et al 1972 Williams and Goldspink 1973 Williams and Goldspink 1978 Scott 1994 However muscle length adaptation is not well enough understood to be incorporated as automatic Orbit calculations To predict long term eye alignment you must make your own hypotheses about such secondary muscle length changes and enter your estimates into Orbit In the Tutorial section below we will show how this might be done Even less is known about post surgical modifications of innervation and about fibrotic and atrophic changes that may occur in some situations As with secondary muscle length changes you can enter any such changes you suspect and Orbit will deduce their consequences 1999 09 04 A Biomechanical Approach 23 Manipulating the Muscle Model To simulate abnormalities treatments and effects of healing Orbit allows you to alter parameters of the muscle model Various scaling and offset operations on the normal force surfaces are available Normal Contractile Normal Elastic Muscle Force Muscle Force MI U S C eC p Force an Model 2 v Innervation Offset Ss Force g How Eye Parameters Affect Muscle Force Surfaces D OO I ON mi translation ojo 0 js nnervation aN Sensitivity Wo a 150 14 per i 125 Z E t compression Oo
71. ect in the menu bar or in an Orbit window titles labels buttons to find out what it is and how to use it untitled 7 Normal Left Eye Parameter Editor s ich a a s i n uart 5 MME Click to set all parameters shown to Values characterizing 4 lateral rectus muscle normal eye medial rectus muscle superior rectus muscle Window remains open see inferior rectus muscle the insertion Tine fro superior oblique muscle its normal location 1 l l l j inferior obligue muscle mm along the surface the globe Create a new simulation Orbit help Close Simulation Fixing j hiya eye i parameters will be balloons tell Close Window w normal Both can be about Save do subsequently modified strabismus and Save AS bio mechanical modeling as well as about using Orbit Page Setup Print One Print Turn Balloon Help on when you first use a window and when you do not understand a menu selection window field or button Then turn it off 1999 09 04 16 Orbit 1 8 User s Manual Help on the Menu Bar When Orbit is active several short discussions are available About Balloon Help online by clicking Help in the Menu Bar at the top of your Macintosh screen Show Balloons Whatis Orbit p Not Enough Wiemory Help What is Orbit contains Bibliography an overview Ordering Orbit
72. els Suppress alerts about solutions not found can be checked if you don t wish to be notified when one or more gaze angles fail to converge 1999 09 04 Orbit Reference 87 The AlignVu tab contains preferences for the Alignment Viewer window Both Eyes Alignment Viewer Align Yu Alignment Yiewer Preferences Alignment Chart Fet Simulation Fef Measurements Deviation Chart ie Simulation ca Measurements Intended Gazes Near the top of the Alignment Viewer is a Hess Lancaster type Alignment Chart which always shows intended gazes and optionally shows simulated positions of the following eye blue o and measurements red o Below the Alignment Chart is the tic tac toe Deviation Chart Deviations are differences between actual and intended gaze positions Choose whether to view simulated deviations of the following eye or measured deviations Choose which deviations to show by their intended gaze If you have not selected some chosen positions with the Intended Gaze Selector the chart will show blank boxes The Param Fit tab contains preferences for the Parameter Fitter window Both Eyes Parameter Fitter that allow you to modify the fitting method Param Fit Parameter Fitter Preferences Criterion is Mean Error ca Max imum Error Werghts Horizontal 1 vertical 1 Torsion ol ol Convergence Failures Allowed et Beep when do
73. engthening or post surgical healing Miller JM 1989 Functional anatomy of normal human rectus muscles Vision Res vol 29 isu 2 pgs 223 240 The actions of extraocular muscles depend on their positions as a function of gaze These positions vary with muscle forces which are normal only in alert subjects making voluntary fixations Magnetic Resonance Imaging MRI was used to view normal human orbits with voluntary gaze varied over a circular field 77 deg in dia centered on the orbital axis Computer aided reconstructions reflecting the data of four normal adult subjects produced clear pictures of the rectus muscles and optic nerve and yielded data on muscle paths and cross sections From their origins in the orbital apex to their points of tangency with the globe rectus muscle side slip relative to the orbit is approximately zero consequently their muscle planes though not necessarily their axes of rotation are approximately fixed in the orbit As the rectus muscles contract they draw in towards the orbital axis and as they relax they bow outwards this excursion is as large as 3 7 mm Contraction also tends to cause the planes of maximum cross section to move posteriorly Miller JM Robins D 1987 Extraocular muscle sideslip and orbital geometry in monkeys Vision Res vol 27 isu 3 pgs 381 92 The belly of each extraocular muscle is elastically coupled to both the globe and orbit The dependence of muscle planes on
74. er Read this help window if you have not already done so Es Otherwise to be sure you can follow the examples below close any open windows select Both Eyes Preferences for New Simulations click Faetery and then Preferences for Hew Simulations heneral Preterenrec gt Then create a new simulation with File New The Alignment Viewer will open It should look like this _ _ _ _ _ _ _ SSS oJ untitled EFES ies Alignment iewer en m Gwn nr lt lt doa iss Morr a Chart type lancaster fick rel LEFT EYE right eye fixing LIF RIGHT EYE Cleft ewe fixing 40 30 lJ E t E a zZ d J eye AE 40 30 40 10 O 10 20 30 40 40 on 4O 40 30 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude Intended Simulation Cyclorotation s 5 On this Hess Lancaster type chart each intended gaze position is represented as a small black cross in the 1999 09 04 50 Orbit 1 8 User s Manual intended position of the following eye that is the position that would be assumed by a normal following eye Positions of the following eye are shown as blue circles 0 with connecting lines to emphasize the pattern An arrow through each circle shows cyclorotation torsion in excess of normal Listing s Law torsion as tilt from straight up multiplied by 5 for visibility The simulated eyes are normal because we haven
75. er tabs appear in both preferences windows The Sim tab contains preferences that apply to an entire simulation Preferences for EXER Factory Active Simulation Simulation Preferences User Level O Novice J Experienced E Expert L Intended Gaze Selector Lett Eye Parameter Editor Live Eyes Ei ligament Wiewer Right Eye Parameter Editor L Parameter Fitter L Show gaze angle differences in prism diopters CA L Suppress alerts about solutions not found User Level At lower User Levels options are limited to highlight basic operations Novice users are not offered certain windows at all they are dimmed in the Menu Bar others appear in simplified form Experienced users are offered all windows but three of them the Measured Gaze Editor Mechanical State Viewer and Eye Parameter Editor appear in simplified forms Almost all users of Orbit will begin at the Novice and then advance to the Experienced level It is not allowed to lower the User Level of an existing simulation because this could make inaccessible some values previously modified Open with Simulation Have the windows you always use open automatically On a slow machine it may take significant time to open large or graphic windows and windows that require the simulation to update Show gaze angle differences in prism diopters This will appropriately change the deviation values shown in various windows and their unit lab
76. erent fiber types in extraocular muscle may be central to the characteristics exhibited by the muscle during saccades iii the transient properties of lengthening muscle such as yielding are not 1999 09 04 150 Orbit 1 8 User s Manual significant during saccades and iv the series elastic component in active muscle may be predominantly generated by the elastic properties of the cross bridges 1999 09 04 Literature Cited 151 Literature Cited Clark RA Miller JM Demer JL 1997 Location and stability of rectus muscle pulleys inferred from muscle paths Invest Ophthalmol Vis Sct vol 38 pgs 227 240 Collins CC Carlson MR Scott AB Jampolsky A 1981 Extraocular muscle forces in normal human subjects Invest Ophthalmol Vis Sci vol 20 isu 5 pgs 652 64 Collins CC O Meara D Scott AB 1975 Muscle tension during unrestrained human eye movements J Physiol Lond vol 245 isu 2 pgs 351 69 Demer JL Miller JM 1995 Magnetic resonance imaging of the functional anatomy of the superior oblique muscle Invest Ophthalmol Vis Sci vol 36 isu 5 pgs 906 13 Demer JL Miller JM Koo EY Rosenbaum AL 1994 Quantitative magnetic resonance morphometry of extraocular muscles a new diagnostic tool in paralytic strabismus J Pediatr Ophthalmol Strabismus vol 31 isu 3 pgs 177 88 Demer JL Miller JM Koo EY Rosenbaum AL Bateman JB ed 1995 True versus masquerading supe
77. ermined by Listing s Law If the fixing eye had significant abnormal torsion then Orbit s assumption of Listing torsion would produce errors in simulated following eye positions For instance if the fixing eye were actually extorted eg SO palsy Orbit would still suppose eg that the medial rectus muscle MR of the fixing eye had only horizontal action in primary position and innervate the following eye on that assumption Actually the MR of the extorted fixing eye had developed some elevating action requiring general alteration of innervations to the fixing eye and so by Hering s Law to the following eye Thus the simulation of following eye positions would have been in error 1999 09 04 A Biomechanical Approach 45 PowerMac computers perform these computations quickly If you are using a Non PowerMac you will need to be very patient and pay close attention to the issues discussed in the section of this Manual on Speed 115 We do not recommend you use Orbit on a Non PowerMac except for evaluation 1999 09 04 46 Orbit 1 8 User s Manual 1999 09 04 Tutorial 4y Tutorial Examples As with any tool Orbit s utility depends on your skill To show you how to work with Orbit we will develop several simulations These simulations are saved in the L50 Palsy Example RLA Palsy Example and Duane Syndrome Examples folders for your examination We will point out the s
78. ers HV Glasgow BJ 1995 Evidence for fibromuscular pulleys of the recti extraocular muscles Invest Ophthalmol Vis Sci vol 36 isu Invest Ophthalmol Vis Sci pgs 1125 36 PURPOSE Magnetic resonance imaging MRI shows that the paths of recti extraocular muscle EOM bellies remain fixed in the orbit during large ocular rotations and across large surgical transpositions of their insertions These findings imply that recti EOMs pass through pulleys coupled to the orbit and anterior to the muscle bellies because the insertions must move with the globe The present study was conducted to locate anatomically and to characterize histologically the pulley tissues METHODS High resolution MRI images were collected from volunteers using multiple gaze directions to infer the locations of and occasionally to visualize recti EOM pulleys Fresh cadaver orbits were exenterated and dissected to evaluate mechanical and structural properties of the orbital connective tissues Lipid was cleared from whole specimens to reveal tissue relationships Other specimens were selectively step and serial sectioned for histochemical and immunohistochemical staining RESULTS Magnetic resonance imaging demonstrated dense connective tissue structures within posterior Tenon s fascia near the equator of the globe adjacent to the recti EOMs Histochemistry showed these structures to be pulleys fibroelastic EOM sleeves consisting of dense bands of collagen and elasti
79. es a new n dimensional position for the worst fit point and calculates the new error When the simplex encloses a point of relative minimum error it tends to shrink and when it s small enough the algorithm quits Thus during terrain mapping parameter values and Current Error will normally change and then change back A new n dimensional guess may increase Current Error because it reflects the worst of three points n dimensional parameter sets and because of poor guesses 1999 09 04 102 Orbit 1 8 User s Manual Measured Gaze Editor In the SO palsy simulation above we imported a file of clinical measurements It is also possible to enter clinical measurements individually from the keyboard To do so select Right Eye Measured Gaze Editor and choose all gaze positions for which you have data use shift click to select contiguous multiple items or command click to select disjoint multiple items and click _oK_J Title bars of the Measured Gaze Editors like those of Mechanical State Viewers are labeled with the intended gaze position of the following eye that is the position a normal following eye would have gone to For example intended gaze 30 30 corresponds to fixing eye gaze 30 30 because when the fixing eye abducts positive the following eye adducts negative Ifa cyclorotation is unknown leave the excyclo rot field blank not 0 untitled z 30 30 Right Eye Measured Ga
80. eti Inner Eye Parameters The right eye could not fixate some positions you requested Remove the corresponding left eye intended gazes or try again with different right eye parameters Solutions were not found for some right eye gazes results shown are OK Some innervation sets were not found Fixing Eye an for the fixing left eye Parameters Solutions were not found for some left Different left eye paramete eye gazes results shown are OK eg set Contractile Muscle 1 instead of 6 Some innervation sets were not found for the fixing right eye l i Tp Different left eye paramete eye gazes results shown are OK HE Some fixing right eye innervation sets Intended Position frustrated the Hering s Law calc of fixing Eye Different right eye parameters may help Reflect Eye Position Across Midline Intended Position of Following Eye Find Innervation Set Solutions were not found for some left eye gazes results shown are OK Some innervation sets were not found for the following left eye Solutions were not found for some right Different inner eye parar eye gazes results shown are 0K Inner Eye help Parameters Some innervation sets were not found for the following right eye Different inner eye parameters may z
81. f syndromes eg Bregman Ly and Galetta 1991 and no tables of surgical dose response relationships eg Parks 1975 Such empirical generalizations are only useful in typical situations and do not help understand underlying mechanisms Instead Orbit can produce strabismus demonstrations and derive dose response relationships Orbit is not an expert system An expert system is a model not of the topics of interest themselves innervations muscles etc but of the inferences and judgments of human experts One could create as many different strabismus expert systems as there are strabismus experts Indeed Orbit knows nothing about strabismus except insofar as strabismus can be modeled as failures of normal binocular coordination 1999 09 04 4 Orbit 1 8 User s Manual Is Orbit Difficult to Use Yes and no As a Macintosh program Orbit is simple and easy to use If you know a few other Mac programs learning Orbit will be easy However if you are new to biomechanical analysis you may find it quite unlike your current approach to strabismus Although you will not need to learn mechanics mathematics or anything not in this manual you will need to sharpen your analytic thinking in several areas as you will see Why bother If you believe biomechanical analysis to be an academic exercise or passing fad you will probably not want to make the effort necessary to understand this new approach Howe
82. gaze angle must be determined experimentally In monkeys radio opaque markers were implanted along the upper and lower margins of a lateral rectus A scleral search coil was implanted in the other eye With the eye in various gaze positions X ray images were made to show the LR in the lateral view We found that as the eye rotates vertically over 50 deg 25 deg the point of tangency of the LR with the globe slips an average of 5 1 mm vertically with respect to 1999 09 04 Annotated Orbit Bibliography 145 the globe allowing this point and so the muscle plane to remain approximately fixed relative to the orbit The results of quantitative orbital dissections are presented in support of the sideslip calculations 1999 09 04 146 Orbit 1 8 User s Manual Clinical Application of Biomechanical Modeling Clark RA Miller JM Rosenbaum AL Demer JL 1998 Heterotopic muscle pulleys or oblique muscle dysfunctionfournal of the American Association for Pediatric Ophthalmology and Strabismus vol 2 pgs 17 25 INTRODUCTION The description of connective tissue sleeves that function as pulleys for the rectus extraocular muscles EOMs suggests that abnormalities of EOM pulley position might provide a mechanical basis for some forms of incomitant strabismus Pulleys determine the paths and thus the pulling directions of EOMs METHODS High resolution coronal magnetic resonance images MRI spanning the orb
83. ged by changing a connection weight D 2 2 0 om mm D D om mm D2 a0 D A Our theory of Duane s Type I may be expressed as follows Brain Motor Nucleus Connection Weights of nuclei s total excitation Abducens 0 T T T T T CculosMR 75 100 0 0 T 0 Dculo SR T D 100 0 T T Dculo IF T D T 100 T T Trochlear E J E J 100 J 0 g E E 0 100 Ocula 10 1999 09 04 Tutorial 79 Note the shadows on the two modified cells A cell is shadowed when you modify it either by typing a new value or clicking Nermat Shadows are retained until you depart from the window and indicate which values would be affected by clicking Revert ES A look at the Alignment Viewer shows that the rotational defects of Duane s Type I signs 1 3 and 5 above are all reflected in the simulation UF RIGHT EYE Cleft eye fixing Note that up shoots and down shoots emerge naturally from co contraction in adduction essentially in accord with the theory advanced by Souza Dias 1976 OTA OWA ea cee ro Does the pattern of globe retraction also fit clinical en AO 40 30 20 10 10 20 30 40 AB expectations Horizontal Gaze deg longitude R Select Right Eye Mechanical State Viewer and open the windows for intended gazes 40 0 20 0 0 0 20 0 and 40 0 you can select them all at once by holding down the key as you click on items in the list you ll need to scroll the wi
84. gnment in the later This occurs because without pulleys the transposed vertical recti acquire actions similar to the RLR except they are innervated in up and downgaze 1999 09 04 Tutorial 77 Duane s Retraction Syndrome Following Huber 1970 von Noorden 1990 characterized three varieties of Duane s on the basis of clinical signs Are there three corresponding mechanisms Let s explore this question with some new simulations ES To begin check that your User Level is Experienced select Both Eyes Preferences for New Simulations click the 5im tab and check that the Experienced button is pressed The Parameter Editor provides a more convenient way than the Live Eyes to modify connections between motor nuclei and muscles Click to confirm your changes ES Begin a new simulation with File New and set the following intended gazes oy Duane 1R S FT H A Bes Alignment Yiewer Duane Type 1 Right Eye Doo oOo o o Gyn nm Sim Meas miog doolloo Horm 19990305 Chart type lancaster fick rel ight eve fixing LIP RIGHT EYE left eye Uo Mot Chane Mone Uo Not Change Mone Primary Position l Primary Position Ht30 430 W430 430 t Ht30 430 v30 430 Ht30 415 W430 415 G Ht30 415 V430 415 Ht30 415 V309 415 ne aq Ht30 415 VWtS0 415 ne Ht40 420 Vado 20 s H40 420 Vado a20 HE40 420 w40 420 ne j H40 420 Ved 420 ne Ht40
85. gure is a schematic of the Lancaster Test in which the eyes are dissociated by viewing colored targets through colored filters The patient has been asked to fix the red bar at 0 0 seen only by her left fixing eye and to move the green bar seen only by her right following eye so that it appears to lie on top of the red bar Assuming normal retinal correspondence the positions of the two bars give the gaze angles of the two eyes If binocular alignment were normal our patient would have superimposed the two bars In the case shown her right eye is 20 exo deviated misaligned outward 5 hyper deviated upward and somewhat excyclo deviated twisted top outwards around the visual axis Orbit s simulation schematized below follows the clinical test beginning with the fixing eye 1999 09 04 36 Orbit 1 8 User s Manual First Figure part A the operator Find Fixable Position calculates the torsion that the possibly abnormal fixing eye would assume at a chosen 2 dimensional gaze angle Then B with all 3 gaze coordinates we can find the innervations that would bring the fixing eye to that position To implement Hering s Law Orbit 1 8 Binocular Model C we use Inner Eye f Find torsion for 2D Gaze a Position arbitrary fixing eye new in Orbit 1 8 Parameters to A Innervation Set lay aa in ixapie to FIXINg Eye Inner Eye 3D Position into position Parameters spac
86. hanging RMR Relative Stretch Sensitivity from 125 representing contracture to 100 representing a muscle that stretches normally iS Finally to facilitate comparison we use Both Eyes Gaze Selector to remove from the simulation those gazes for which we do not have measurements RLR Palsy PstOp sim 2 LEFT EYE right eye fixing UP FIGHT EYE Cleft ewe fixing OTA WA ea ao 30 40 10 O 10 20 30 40 40 al 40 40 s0 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude The simulation achieves a good match with the clinical measurements Some improvement in right eye horizontal range has been achieved although not enough to normalize primary position As expected some vertical range has been lost The main clinical problem remaining is the primary position misalignment which might have been better managed by transposing RSR and RIR with posterior sutures Foster 1996 1999 09 04 Tutorial ES We can visualize the post operative eye with Right Eye Graphic Eyes Here is the right lateral view of the right eye with the left eye fixing 0 0 oma mai 1 yaWaiaies Parise T r i al ma i Ni navi bbe et Hine emeeee 2 m aL tty LULU LLC ak AA LN AU G T T ana n r TH Tene ilip ANANIN s He iil Ii nie eis He aU LA ge ui l nee THINE HH fall br Prva GHH Ter hil a Era a Ds We began by mentioning that this
87. heir pre operative positions Magnetic resonance imaging before and after transposition clearly supported the pulley model the paths of rectus muscle bellies remained almost fixed in the orbit despite large surgical transpositions of their insertions What s holding the belly A Ya back 2 5 Fah PON r oe ba s pe 1 j Because there was some movement of the muscle belly we termed the new constraints soft pulleys a 1999 09 04 Orbit 1 8 User s Manual 5 Histochemistry What was holding the muscle bellies back We conducted a series of studies to anatomically locate and histologically characterize the pulley tissues Demer Miller Poukens Vinters amp Glasgow 1995 Fresh cadaver orbits were exenterated and selectively step and serial sectioned for histochemical and immunohistochemical staining Dense connective tissue structures within posterior Tenon s fascia near the equator of the globe adjacent to the recti EOMs were found to be sleeves consisting of dense bands of collagen and elastin suspended from the orbit and adjacent EOM sleeves by bands of similar composition A monoclonal antibody to human smooth muscle a actin demonstrated substantial smooth muscle in the pulley suspensions and in posterior Tenon s fascia Mid orbital and posterior coronal sections can be schematized as follows Horizontal Anterior Slings a ae smooth SR Muscle M p C O
88. help Innervation set j to Following Eye A Solutions were not found for some left eye gazes results shown are OK Some positions of the following left eye were not found Following Eye Parameters Find Position Solutions were not found for some right Try again with different left eye gazes results shown are OK parameters Some positions of the following right eye were not found Position of Try again with different right eye parameters Following eye 1999 09 04 Orbit Reference 119 Another type of alert means that an unacceptable eye parameter was entered or the biomechanical model attempted a mathematically improper operation like dividing by 0 Accumulated rounding errors and of course programming errors can cause this The following alert appears The biomechanical model could not handle the eye parameters and gaze positions you specified Change something and try again 1999 09 04 120 Orbit 1 8 User s Manual Not Enough Memory Orbit will tell you if it cannot complete a request because of insufficient memory Here are some things to try in the order you should try them A similar procedure is useful in solving memory problems with any Macintosh application 1 Close some Orbit windows and try your request again 2 Go to the Finder eg by clicking on the Desktop select amp About This Computer
89. ifference is that the second request does not offer any options and just quickly prints one copy of the entire selected window 1999 09 04 118 Orbit 1 8 User s Manual Trouble Solutions Could Not Be Found Orbit may fail to converge on a solution This may be because you have chosen unrealistic parameters check for a typo or try a value closer to Nermal extreme gaze positions or because of limitations in the solution methods we use Alerts suggest how to solve the various kinds of convergence problem The figure below shows the stage of calculation that can produce each alert Orbit 1 8 Binocular Model with Possible Alerts 2D Gaze Position Find Fixable 3D Position Fixable Position Find Innervation Set Different right eye parameters may help eg set Contractile Muscle Innervation set to Fixing Eye Strength to 1 instead of 6 Solutions were not found for some right A eye gazes results shown are OK Inner Eye Find Parameters Position a fixing left eye innervation sets rustrated the Hering s Law A Solutions were not found for some left Solutions were not found for some right eye gazes results shown are OK The left eye could not fixate some positions you requested Fixing Eye Parameters Solutions were not found for some left Remove the corresponding eye gazes results shown are 0K intended gazes or try agai different left eye param
90. illustrate the application of the method in diagnosis and surgery It also offers for the first time a quantitative estimate of the multitude of ways in which muscles can interact and interfere with each other when they hold the globe Two of the results are interesting because muscles have different lengths and sizes their innervational participation in a movement can appear to be quite different than their mechanical participation From an innervational standpoint the vertical recti and obliques participate equally in vertical gaze Muscles interfere with each other a good deal and necessitate changes of innervation to counteract these cross couplings This causes unexpected dependencies of innervation on eye position and leads for example to the fact that the superior rectus innervation in up gaze is just as large in adduction as in abduction 1999 09 04 138 Orbit 1 8 User s Manual Studies of Eye Muscle Forces Paths amp Pulleys Clark RA Rosenbaum AL Demer JL 1999 Magnetic resonance imaging after surgical transposition defines the anteroposterior location of the rectus muscle pulleys J AAPOS vol 3 isu 1 pgs 9 14 INTRODUCTION Connective tissue pulleys serve as the functional origins of the rectus extraocular muscles EOMs and constrain the sideslip of the posterior EOM bellies after transposition surgery Anterior to the pulleys EOM paths appreciably displace to reach their transposed insertions The
91. increased stretch 1999 09 04 20 Orbit 1 8 User s Manual increased elastic and altered contractile force components of the RLR It then computes the forces in the antagonist RMR and other muscles of the right eye needed to hold the eye in primary position and the innervations needed to produce the contractile components of these forces Having computed right eye innervations Orbit uses its notion of Hering s Law to compute innervations to the following left eye left eye muscle forces and finally left eye position With the operated right eye following innervations determined by the unoperated fixing eye are assumed unchanged from before surgery Resection alters RLR forces and so the right eye s position Orbit calculates the new forces and eye position as well as more subtle things such as changes in muscle path shape and translational globe position Note that if you disinsert a muscle cut off 5mm and sew it back to the original scleral insertion Orbit cannot know that you lost Imm during disinsertion and took a Imm bite of the remaining tendon during reinsertion In this case you actually did a 7mm resection and must reduce Tendon Length from 8 4 to 1 4 mm Now suppose we resect more than the tendon length shorten the muscle proper Elastic Force stiff vs soft Resection shortens a muscle and a short muscle is said to be stiff What does this mean Imagine taking a
92. ion gt Here is how to simulate the RIR recession Continue from where you imported the post operative measurements or Open LSO Palsy PstOp sim 0 Open the Live Eyes window choose the Inferior point of view and click the RIR tendon The figure of the pop up window below shows the Help Balloon to remind you that movement forward is along a longitude line from the eye s posterior pole to its anterior pole and movement around is along a perpendicular latitude line L50 Palsy PstOp sim 1 Muse Insert Movement around mm from normal forward The Muscle Insertion Movement shown above is 4 1 mm as reported by the surgeons But we must also account for tendon lost during disinsertion and reinsertion We estimate that 2 mm are lost and reduce RIR tendon length from 5 4 to 3 4 mm 1999 09 04 Tutorial 63 Compared to postsurgical measurements the simulation is still left hyperphoric especially in downgaze LSO Palsy PstOp sim 1 LEFT EYE right eve fixing UP FIGHT EYE Cleft eye fixing OTA WA oo ea eo m AB 40 30 40 10 O 10 20 30 40 40 ee 40 40 30 20 10 0 10 20 230 40 AB Horizontal Gaze deg longitude R To complete the postsurgical simulation we need to simulate the LIO recession performed on these patients Buse Insert Movement around mm from normal forward Muse Insert Rotation 7 Tendon Length mm Tendon Width mm 1999 09 04 Orbit 1 8 User s
93. itial value taken by the fitting procedure It is set to the current value by default If you have a better guess enter it since it is best to begin fitting with eye parameters close to those desired The less distance in parameter space the algorithm has to traverse the less likely it is to get trapped in a local minimum and quit with unsatisfactory parameters Min and Max are lower and upper limits on parameter values the Fitter will try They are empty by default meaning no limits If the Fitter wanders into implausible values constrain it by setting these limits The alert The biomechanical model could not handle the eye parameters means that the fitter has tried frankly illegal values such as a negative muscle length or strength You can dismiss the alert and fitting will continue It might be better to set Min and Max values to keep the fitter out of trouble A parameter s initial value will be forced to lie between the two limits The Fit field shows the parameter value arrived at by the fitting procedure While the Fitter is running it 1999 09 04 Orbit Reference 99 shows the values tried When the Fitter is done it shows the best value found Settings modify Criterion Q Mean Error CD Maximum Error the fitting method Weights Horizontal 1 vertical 1 Torsion al Drag a parameter _O Convergence Failures Allowed from the Parameter Editor R Beep when done and drop it into
94. its were obtained in primary position upgaze and downgaze for each subject Paths of the EOMs were measured with reference to the orbital center and permitted inference of pulley locations RESULTS Data from 18 orbits of orthotropic subjects defined means and standard deviations of normal EOM pulley coordinates Eight patients ages 17 60 years had heterotopic EOM pulleys defined as displaced at least two standard deviations from normal We found one to eight heterotopic pulleys considering both orbits in each of four patients who had been diagnosed with marked superior oblique SO overaction and mild to marked inferior oblique IO underaction Each patient had superior mislocation of at least one lateral rectus LR pulley by 1 8 4 9mm Three patients diagnosed with mild to moderate IO overaction and mild to moderate SO underaction in only one orbit had one to three heterotopic EOM pulleys Each of those patients had at least one LR pulley inferiorly dislocated by 1 9 4 9mm The final patient who was diagnosed with mild IO underaction and normal SO function bilaterally had bilateral superior mislocation of the medial rectus pulleys by greater than 2mm Computer simulations using the Orbit program incorporating individually measured pulley positions reproduced the clinical patterns of incomitant strabismus in all cases without postulating abnormalities of oblique muscle innervation or contractility CONCLUSION Heterotopic EOM pu
95. itter Calculations are much simpler and faster if the fixing eye is normal With a slow computer try to work with only one abnormal eye and to have that eye be the following eye only That is do not simulate secondary deviations Windows like the Parameter Editor and the Mechanical State Viewer may take a moment to open because of the large number of fields they contain particularly at Expert level But there is no need to close them and re open them for each use just leave them open The time it takes for the biomechanical model to run is proportional to the number of fixation points chosen Use the Intended Gaze Selector to reduce the number of gaze positions to the minimum needed Printing You can print Orbit windows to record patient data intermediate simulation stages or simulation results We find it most useful to print the Alignment Viewer which contains patient and simulation identifiers alignment measurements simulation results and notes To print the Alignment Viewer select it and then select File Print This request elicits the usual Macintosh Print Dialog allowing you to choose the pages to print the number of copies and other options Parameter Editors and Mechanical State Viewers cannot be printed in this way Instead use the Export commands eg Left Eye Export Eye Parameters to create a text file and then edit and print the file as desired with a text processing or sp
96. kes it a useful tool for testing hypotheses about such adaptational mechanisms 1999 09 04 22 Orbit 1 8 User s Manual In summary removing a length of muscle affects both elastic and contractile components of muscle force e A resected muscle exerts more elastic force at a given length and so roughly speaking at a given eye position This effect is most significant when the muscle is elongated that is out of the muscle s field of action It is in this sense only that a resected muscle is stronger e Resection of a muscle that removes contractile tissue leaves the muscle less effective in contracting A given change in innervation results in less change in path length and the range of lengths over which the muscle can effectively operate recall the sliding filament model is reduced These contractile effects are most important in a muscle s field of action So with respect to the above discussed effects of muscle manipulation you specify the surgery and any muscle abnormalities and Orbit does the rest Secondary Effects of Surgery As we have seen resection stretches a muscle forcing its sarcomeres to operate at longer than optimal lengths Conversely recession slackens a muscle forcing its sarcomeres to operate at shorter than optimal lengths It has been found that within a few weeks or months resected muscles actually add sarcomeres and recessed muscles delete sarcomeres ther
97. lation file and so will be in effect the next time the simulation is opened Other simulations on disk or open but inactive in the background are unaffected Some open windows of the active simulation are also unaffected Window Settings WAHE affect only the current instance of the window containing the Window Settings button This allows one eg to quickly change values displayed in an Alignment Viewer or structures shown in a Graphic Eye without changing anything permanently Window Settings are lost when the window is closed and subsequent behavior is determined by Preferences for Sim 1999 09 04 Orbit Reference 123 Where are normal muscle insertion coordinates They are in the Mechanical State Viewer SSS untitled 0 0 SS H Rotated Muscle Insertion mm from globe center lateral 10 1 Ei ez les Zal 3 9 anter ior D a 5 5 Bie r Q B 1 10 4 SUper ior 0 0 0 0 10 6 10 1 10 4 2 6 Rotated Muscle Insertions are the centers of the insertion lines in the familiar head fixed anatomic coordinate system for the current gaze angles m 5 ee PPS a fe rs r _ Usually you will want to know insertions in primary position as shown above note 0 0 in the title bar How do I make an Orbit Movie All you need to make movies yourself is Apple s upgraded QuickTime Movie Player or some other utility that can read a folder of PICT files and
98. led by increasing contractile muscle strength Expert note Your Parameter Editor shows Contractile Muscle Strength and Contractile Muscle Relative Strength Normally the former values are all 100 and the later give contractile forces relative to the lateral rectus muscle LR The two strengths are separated so you can think about changes with respect to either a muscle s normal strength alone or relative to other muscles Internally the two values are simply multiplied so eg doubling either has the same effect Stretch sensitivity and elastic strength allow the normal elastic muscle force surface to be customized e Stretch Sensitivity squashes the Elastic Force Surface along the stretch axis A fibrotic muscle which hits asymptotic stiffness the leash region at low values of stretch would be modeled by increasing Stretch Sensitivity 1999 09 04 A Biomechanical Approach 25 e Elastic Strength scales the vertical force axis A large muscle with more elastic fibers in parallel than normal would be modeled by increasing elastic muscle strength Expert note Your Parameter Editor shows Elastic Muscle Strength and Elastic Muscle Relative Strength Normally the former values are all 100 and the latter give elastic forces relative to the LR The two strengths are separated so you can think about changes with respect to either a muscle s normal strength alone or relative to other muscles
99. left and those of the right eye on the right following the perspective of the Alignment Chart Abducting and adducting directions are as labeled near the top of each panel the nose is between the two panels All angles are in degrees Consider eg the gaze position for which the right eye will attempt to abduct 30 and elevate 30 In terms of the Hess Lancaster test this means that the patient will be instructed to adduct 30 and elevate 30 with the fixing left eye If both eyes are normal the following right eye will go to the intended positions exactly Otherwise it may go somewhere else Remember that to Import clinical measurements Left Eye Import Measurements Or Right Eye Import Measurements the intended gaze angles must already be in the simulation eg chosen in the Intended Gaze Selector 1999 09 04 92 Orbit 1 8 User s Manual Alignment Viewer Use the Alignment Viewer to view simulation results and measurements Info Fields The top part provides fields to record patient and simulation information and shows the alignment chart Help balloons Help Show Balloons associated with the patient and simulation information fields suggest how these fields may best be used L50 Palsy Preop sim 0 Alignment iewer Farm mir on Left ae Oblique Palsy Dog los Gyn nm wallace Pre Op Saas 0 Sim Ja O Meas alot alza 1359 l Norm 19990531 Chart
100. lleys can cause patterns of incomitant strabismus that have been attributed to oblique muscle dysfunction Even isolated mislocations of less than 2 mm coupled with smaller mislocations of the other pulleys can produce the clinical appearance of bilateral oblique dysfunction Pulley heterotopy should be considered in the differential diagnosis of incomitant strabismus and oblique dysfunction 1999 09 04 Annotated Orbit Bibliography 147 Demer JL Poukens V A CR Miller JM Porter JD 1998 Molecular mechanism of strabismus in Marfan syndrome Deficient fibrillin destabilizes extraocular muscle pulleys Abstracts of 24th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus pgs 2 Foster RS 1997 Vertical muscle transposition augmented with lateral fixation JAAPOS vol 1 num 1 pgs 20 30 Demer JL Miller JM Poukens V 1996 Surgical implications of the rectus extraocular muscle pulleys J Ped Ophthalmol Strabismus vol 33 isu 4 July Aug pgs 208 218 PURPOSE Magnetic resonance imaging MRI shows that the paths of recti extraocular muscle bellies remain fixed in the orbit during large ocular rotations and across large surgical transpositions of their insertions This stability of muscle paths is due to their passage through pulleys which are coupled to the orbit and located anterior to the muscle bellies near the equator of the globe Autopsy studies have shown the pulley
101. longitude Our aim is now to match the simulation to the post operative measurements 1999 09 04 60 Orbit 1 8 User s Manual on an an ee ae ee es a os Se Lo AB 40 Avoid a Poor Treatment Note to follow this section on your computer you would need to advance your User Level to Experienced to gain access to the Mechanical State Viewer see Orbit Reference Preferences below Alternatively you could just read this section An SO tendon tuck might seem worth a try Simulation shows however that shortening the LSO tendon by 10 mm corrects hypertropia in up and level gaze but gives little improvement of left eye depression in the important downgaze reading positions LEFT EYE right ewe fixing UP FIGHT EYE Cleft eye fixing PE B niire poagn OTA HAN m D I m 30 20 10 O 10 20 30 40 40 ii A0 40 30 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude Orbit helps understand why this is a consequence of the SO s impaired contractility and normal elasticity Before tucking the SO tendon we opened Left Eye Select Left Eye Intended Mechanical State Viewer and Gaze Position s choose the most hyperphoric Hor iz 7 vert 5 left eye downgaze position Downgaze particularly in adduction is the LSO s field of action its elastic force is therefore always low and pS here is near zero Its contractile force because of the paresis is of course zero
102. lovski DS Shamaeva I 1998 Orbit 1 8 Gaze Mechanics Simulation San Francisco Eidactics Orbit 1 8 is a full binocular model meaning that both fixing and following eyes can be arbitrarily abnormal It is no longer necessary that the fixing eye have normal ie Listing torsion A new Parameter Fitter helps you choose Eye Parameters of a simulated alignment that matches clinical alignment measurements Miller JM 1998 Orbit 1 8 Gaze Mechanics Simulation User s Manual Eidactics Suite 404 1450 Greenwich Street San Francisco CA 94109 USA Miller JM Shamaeva I Pavlovski DS 1995 Orbit 1 5 Gaze Mechanics Simulation San Francisco Eidactics Fixing eye can be abnormal so long as it obeys Listing s Law that is has normal torsion Miller JM 1995 Orbit 1 5 Gaze Mechanics Simulation User s Manual Eidactics Suite 404 1450 Greenwich Street San Francisco CA 94109 USA Miller JM Shamaeva I 1993 Orbit 1 0 Gaze Mechanics Simulation San Francisco Eidactics Miller JM Shamaeva I 1993 Orbit 1 0 Gaze Mechanics Simulation User s Manual Eidactics Suite 404 1450 Greenwich Street San Francisco CA 94109 USA Miller JM Robinson DA 1984 A model of the mechanics of binocular alignment Comput Biomed Res vol 17 isu 5 pgs 436 470 A computer model SQUINT of the static mechanics of human eyes is developed and applied to the diagnosis and treatment of defects of binocular align
103. make a QuickTime movie Adobe Premier is a high end package that does this and much more QuickTime Movie Player came with your Mac Launch it and look in the File menu for the Open Image Sequence command If it s not there you may need to purchase the 30 upgrade to Movie Player from Apple 1999 09 04 124 Orbit 1 8 User s Manual To use Movie Player to make a folder of PICS into a movie the PICT files must all be named with the same characters followed by a positive number that tells Movie Player the order in which to string them together eg faden01 faden0Q2 You will probably need to rename the files produced by Orbit Consult the Orbit Reference section on the Graphic Eyes window to learn how to have Orbit make the required PICTs you will need to raise your User Level to Expert How do I Print Orbit Windows Orbit s print commands are in transition and various methods are used to print different windows We hope to simplify things in a subsequent version The Alignment Viewer is printed as a picture PICT with File Print This request elicits the usual Macintosh Print Dialog allowing you to choose the pages to print the number of copies and other options Parameter Editors and Mechanical State Viewers cannot be printed in this way File Print is dim Instead use the Export commands eg Left Eye Export Eye Parameters to create a text file and then for
104. malities intrinsic to an eye but not abnormalities mediated by abnormal innervations eg secondary deviations Graphic Eyes of course show all abnormalities where solutions can be found Live Eyes uses color to determine the structure clicked If it is not responding properly your Macintosh color table may have been altered Graphics applications sometimes alter the color table and are supposed to restore it when they quit or are put in the background but not all do Quitting the offending program usually solves the problem 1999 09 04 Orbit Reference A Parameter Editor The Parameter Editor provides Expert Users access to all Orbit parameters and Experienced Users access to all but some seldom used parameters Novice users are restricted to the frequently used variables given in Live Eyes pop up windows Extensive Balloon Help Help Show Balloons defines all parameters and other terms used in the Parameter Editor Parameter values are changed in the usual way by selecting and editing All non normal values appear in red Values altered during the current visit to the Parameter Editor are additionally marked with a red drop shadow Click to restore these parameters to the values they had when you last left the Parameter Editor The button sets all parameters to normal eye values The Normal field in the upper right corner of the window shows the normal value of the selected parameter Expo
105. mat the file as desired with a text processing or spreadsheet program Graphic Eyes are printed using the Write PICTs option in Preferences or Window Settings Checking this option will create a PICT file in the folder you choose for the current Graphic Eye if you set the flag in Window Settings or for every Graphic Eye you create if you set it in Preferences PICT format files are viewable with many applications such as SimpleText which came with your Macintosh or with most Mac eraphics applications Pop up windows are not printable but the same information can be printed more compactly from the Parameter Editor All the help windows available on the Menu Bar can be printed with File Print although some will be paginated in an ugly way sorry 1999 09 04 Orbit Reference 125 When Credit is Due Orbit software is 1992 1999 Joel M Miller You may not use any parts of Orbit in a commercial product without permission An early version of the computational code SQUINT is in the public domain and will be supplied on request at nominal cost If your published work refers to Orbit or makes use of Orbit simulations you should include a reference to the program version Miller JM Pavlovski DS Shamaeva I 1999 Orbit 1 8 Gaze Mechanics Simulation Eidactics Suite 404 1450 Greenwich Street San Francisco CA 94109 USA This Manual is 1999 Joel M Miller You may not use
106. me and the intended gaze position Expert Users are shown all Orbit variables Experienced Users are shown a reduced set Novice users are restricted to the eye position information in the Alignment Viewer The title bars of Mechanical State Viewers are labeled with the intended gaze position of the following eye the eye whose variables it shows The intended gaze position is the gaze position a normal following eye would have adopted for the corresponding fixing eye position Extensive Balloon Help Help Show Balloons defines all variables and other terms used in the Mechanical State Viewer Variables in the Muscle Forces Tab require some additional explanation Muscle Forces The Muscle Forces Tab in the Expert Level Mechanical State Viewer is used to answer questions such as these e How much force does each muscle contribute to eye rotation as contrasted with eye translation e What is the axis in Cartesian head relative coordinates about which a muscle rotates the eye Researchers interested in how the brain controls eye movement need to know this instantaneous velocity axis e How does each muscle contribute to abduction elevation and extorsion These three rotations describe the Fick coordinate system discussed above familiar to clinicians e Has a muscle lost tangency with the globe Is it now expending force in globe translation at the cost of globe rotation 1999 09 04 Orbit Reference 107
107. ment strabismus Brief discussions of ocular anatomy binocular vision strabismus and its surgical correction and early strabismus modeling are provided for non specialists in these areas Models of muscle force muscle path globe translation and binocularity are developed To illustrate the use of the model in clinical cases it is applied to the diagnosis and surgical treatment of a case of superior oblique palsy The model s implementation under the UNIX operating system is described 1999 09 04 Annotated Orbit Bibliography 137 Robinson DA 1975 A quantitative analysis of extraocular muscle cooperation and squint Investigative Ophthalmology vol 14 isu 11 pgs 801 825 The mechanical properties of human extraocular muscles have recently been described This allows one to use the force balance equation of mechanics to solve for the complete mechanical state of all six extraocular muscles and the passive orbital tissues in any eye position This includes each muscle s force length innervation and unit action vector which describes how its force is distributed to act horizontally vertically and in torsion Most important this calculation method allows one to predict the tropias that occur in an eye subject to any imaginable form of peripheral pathology It also permits by calculation an estimation of the correction that might be expected from any sort of muscle surgery The tight lateral rectus syndrome is used to
108. n suspended from the orbit and adjacent EOM sleeves by bands of similar composition A monoclonal antibody to human smooth muscle alpha actin demonstrated substantial smooth muscle in the pulley suspensions and in posterior Tenon s fascia Tenon s fascia itself was seen to be suspended at its periphery from the orbital walls like a drumhead CONCLUSIONS The human orbit contains specialized musculofibroelastic tissues in and just posterior to Tenon s fascia that serve as compliant pulleys and determine the pulling directions of recti EOMs In this sense the pulleys are the functional origins of the recti EOMs and are determinants of ocular motility Demer JL Miller JM 1995 Magnetic resonance imaging of the functional anatomy of the superior oblique muscle Invest Ophthalmol Vis Sci vol 36 isu 5 pgs 906 913 PURPOSE To study the size and contractile changes of the normal superior oblique SO muscle using high resolution magnetic resonance imaging MRI and to evaluate the abnormalities in these characteristics produced by SO palsy METHODS Multiple coronal MRI image planes were obtained using a surface coil to span the antero posterior extent of each orbit and were repeated in multiple directions of gaze Digital image analysis 1999 09 04 Annotated Orbit Bibliography 143 was used to measure muscle cross sectional area for evaluation of size and contractility RESULTS Data for 16 orbits of 11 subjects without
109. n is relatively exotropic and shows an asymmetry in left and right eye vertical range that is larger than that measured RLR Palsy PstOp sim 1 LEFT EYE right eye fixing UP FIGHT EYE Cleft ewe fixing OTA HAN ea a Ea 30 20 10 O 10 20 30 40 40 A 40 40 30 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude Both of these inconsistencies should be reduced when we account for stretching of the transposed muscles How much are the RSR and RIR stretched ie Open Right Eye Mechanical State Viewer and select primary position 0 0 SSS amp RLR Palsy Pst0p sim 1 0 0 5 8 amp Right Following Eye Mechanical State Yiewer LE ME SR IR So HluscStretch Other Muscle stretch Absolute mm 4 0 Bb 4 10 0 10 1 2 49 eats Muscle stretch Relative of re p 10 2S a1 z9 15 a In a normal eye the superior rectus muscle SR and the inferior rectus muscle IR are stretched only 15 and we suppose that this represents the target of an EOM s length adaptive processes 1999 09 04 4 Orbit 1 8 User s Manual K Use the Right Eye Parameter Editor to increase RSR Relaxed Muscle Length mm from 32 4 to 36 6 and increase RIR Relaxed Muscle Length mm from 34 4 to 39 0 These changes restore RSR and RIR stretch to 15 Finally these patients got some additional procedures to improve horizontal alignment We will simulate the botulinum injection given to one patient by c
110. ndow to select them all I Click to get a cascade of windows one for each fixing eye position containing values for globe protrusion under the E ePos tab As usual the title bars of the Mechanical State Viewers are labeled with the intended gaze position of the following eye that is the position a normal following eye would have gone to For example the intended gaze 40 0 corresponds to fixing eye gaze 40 0 because when the fixing eye adducts negative the following eye abducts positive INN oy Duane 1R 40 0 SOFIE exo dey 36 7 abduct 3 3 protrude 0 3 hyper dew 1 1 elevate 1 1 excoye la dey 1 2 extort 1 2 1999 09 04 80 Orbit 1 8 User s Manual The title of this window indicates that a normal following eye would have been 40 in abduction 40 0 and gives the values for the sick following eye it s highly eso and slightly hyper deviated and shows 0 3 mm of globe retraction A reasonable way to evaluate globe translation is in comparison to the normal eye Intended Normal Eye Duane s I Eye Duane s Horizontal Protrusion Protrusion Relative Gaze Protrusion 40 0 7 1 3 0 6 20 0 5 0 8 0 3 O 0 5 0 4 0 1 20 0 6 0 3 0 3 40 0 9 0 3 0 6 So with respect to globe translation our simulation predicts the expected pattern retraction negative protrusion in adduction and protrusion in attempted abduction However the total range of abnormal axial translation just o
111. ne Choose the Mean Error Criterion if you want the best overall fit across all gaze positions for which measurements have been entered this might allow a few badly fitted positions but is usually the best choice Choose the Maximum Error Criterion if you want the worst fitted position to be as good as possible Weights are values from 0 to 10 which determine the relative ie 1 1 1 is the same as 10 10 10 significance of 1999 09 04 55 Orbit 1 8 User s Manual each gaze angle component in the fitting algorithm A weight of 0 means that the component is ignored in calculating the error that is minimized Thus because torsion measurements can be unreliable its weight is often set to 0 If the torsion component is omitted from a measured gaze point it is of course omitted regardless of the weight It is possible for the Parameter Fitter to try eye parameters that Orbit cannot solve for some gaze angles This may mean parameters are unrealistic measurements are inaccurate or Orbit is flawed You may wish to allow a small number of Convergence Failures so that you can proceed Set Beep when done to be prompted when a fit is achieved Fitting will take longer if you choose parameters from both eyes many parameters or many gaze angles The Graph Ey tab contains preferences for the Graphic Eyes window Graphic Eyes Preferences Show heise efso hirso yf FSR befe ef LGb bef LR hei eRe f eGib ef RLR
112. ns out that in both Fick and Helmholtz coordinates torsion is zero for pure elevation depression and for pure abduction adduction secondary gaze but non zero elsewhere tertiary gaze Further when torsion is non zero it is different in the two systems Interestingly it turns out to be possible to define yet another coordinate system in which torsion for an eye that follows Listing s Law is zero everywhere We find these Listing coordinates useful when discussing how extraocular connective tissue contributes to enforcing Listing s Law see below but not for much else Coordinated innervations incidentally provide the other contribution so if something is wrong with 1999 09 04 A Biomechanical Approach 43 extraocular tissues or with the brainstem non Listing torsions can result Excyclo short for excyclorotation and the directionally uncertain cyclorotation are conventional terms for the amount of torsion in excess of Listing torsion that is for abnormal torsion Cyclorotation describes single eyes and is zero at all gaze angles for normal eyes by definition Extorsion Excyclo Excyclo Dev If you ve made it this far you might as well push on to the end of the section There are three different notions in common use that involve rotation of the eye about its visual axis Often the concepts are not distinguished or one term is used indiscriminately We distinguish the follo
113. o drive a given eye to a given position 2 To where will a given eye move if supplied with a 5 y PP given innervation set Eye parameters include locations of muscle origins and insertions muscle and tendon dimensions innervation length tension relationships and elastic properties of ocular fat and fascia Innervations to the six muscles of each eye are given in arbitrary units All three components of eye rotation are specified abduction supraduction and excyclotorsion Eye translation significant in some disorders is calculated as well Find Find f Position q arameters p nnervation Fit Parameters Finding innervations and positions is relatively straightforward However clinical application needs the ability to find eye parameters Finding eye parameters corresponds to making a diagnosis or choosing a treatment Finding the parameters of eyes that show a given pattern of misalignment or how eye parameters must be altered to restore good alignment is a trial and error process 1999 09 04 A Biomechanical Approach 27 New in Orbit 1 8 is the Parameter Fitter which automates the trial and error process In some cases then Orbit 1 8 can also answer the third question 3 What parameters describe eyes that will move to desired positions under given innervations 1999 09 04 28 Orbit 1 8 User s Manual Rectus Muscle Pulleys In the Orbit 1 8 model rectus m
114. o the orbital wall Autopsy and immunohistochemical studies showed that these soft rectus muscle pulleys were sleeves composed of dense bands of collagen elastin and smooth muscle Demer et al 1995a suspended from the orbit and adjacent extraocular muscle sleeves by bands of similar composition Evidence has been found of sympathetic parasympathetic and nitroxidergic neurotransmission 1999 09 04 Annotated Orbit Bibliography 135 and innervation has been traced to the superior cervical ganglion in monkey Demer et al 1995b Muscle actions under a pulley model Miller et al 1995 are different from those under traditional models Miller and Robinson 1984 Robinson 1975 therefore different control signals are required The pulleys and associated tissues act we believe as a mid orbital suspension passively constraining the globe s rotational freedom to approximate Listing s Law Tonic innervation of pulley smooth muscle stiffens musculo orbital coupling and perhaps pulley innervation is modulated to refine binocular coordination or move Listing s Plane Miller JM Demer JL 1992 Biomechanical Analysis of Strabismus Binocular Vision amp Eye Muscle Surgery Quarterly vol 7 num 4 pgs 233 248 The mechanical elements of the eye positioning system are the globes muscles and various non muscular orbital tissues Their intrinsic complexity variation across subjects and obscuration by adaptive and non mech
115. occurs because of reflection across the midline The Mechanical State Viewer Shows all of the values mentioned for a given intended gaze You may find it helpful to review the above discussion while looking at the Deviations and Eye Rotation values for a tertiary gaze eg 30 20 Limitations of Orbit In Orbit 1 0 the fixing eye had to be normal Orbit 1 5 and 1 7 did not require that the fixing eye be normal only that it obeys Listing s Law that is has normal torsion The following eye could be arbitrarily abnormal With Orbit 1 8 this last restriction is lifted the fixing eye too may be arbitrarily abnormal The method used by Orbit 1 8 outlined in part A of the Orbit 1 8 Binocular Model flowchart above is similar to that described by Miller and Robinson 1984 The reason for the Listing s Law restriction in earlier versions can be explained with reference to part B of the Lancaster Test simulation flowchart In part B we calculate innervations to the fixing eye Find Innervation Sets needs to be given all three coordinates horizontal vertical and torsional of each Fixing Eye Position and all Fixing Eye Parameters to do its work Generally we specify only horizontal and vertical components of the fixing eye position as with the Intended Gaze Selector discussed below and make some assumption about torsion Our assumption in Orbit 1 7 and earlier versions was that torsion of the fixing eye was det
116. on Test of Binocular Alignment were run by manipulating parameters in both left and right eyes Quadra 700 PowerMac 6100 60 iMac G3 266 PowerBook G3 292 PowerMac G3 300 Machines with the PowerPC RISC processor below the line are much faster than the 680X0 based machines they replaced above This is because Orbit spends most of its time doing floating point calculations which are a special strength of the PowerPC Speeds for the G3 and G4 types of PowerPCs should vary with processor speed If you have a slow machine buy enough memory so you don t have to use Virtual Memory Turn off File Sharing See your Macintosh Owner s Manual for information about Virtual Memory and File Sharing System Software Some INITs software placed in the Control Panels or Extensions folders of the System Folder can slow your Macintosh down Experimentation can tell you if a particular INIT ora particular combination of INITs is exacting too high a cost Create folders like Control Panels disabled and 1999 09 04 116 Orbit 1 8 User s Manual Extensions disabled and drag any offending INITs to them Restart your Macintosh to run without the disabled INITs Move them back and Restart to re enable them Programs called extension managers provide an equivalent more convenient way to enable and disable INITs Use of Orbit If you do not have a fast machine you will not want to use the Parameter F
117. onal Force of a muscle acts in each direction We call these values Rotational Force Components 1999 09 04 110 Orbit 1 8 User s Manual a f um Unlike the Unit Moment Vector Rotational Force Components are not defined in a fixed orthogonal coordinate system they are defined in the non orthogonal rotating Fick coordinate system described earlier In consequence abducting elevating and excyclorotating components will not necessarily sum as vector components Indeed component forces may be larger than the Total Rotational Muscle Force If this seems strange consider the game tug of war in which two very large opposing component forces yield a near zero resultant Primary Abduction 1 s a f M m YY f A Hf Myf Uf yj f m m K Regardless of how the eye arrived there a given rotated position is specified in Fick coordinates as though the eye started in primary position and then rotated as follows First the eye is imagined to rotate in abduction or adduction about the earth vertical axis z Second it rotates in elevation or depression about x a new axis which was not defined prior to the rotation about z The axis x is derived from the axis x rotated 1999 09 04 Orbit Reference 111 with the eye about z Finally cyclorotation rotation about the visual axis is defined about y which axis has rotated with the eye through the two preceding rotations
118. ongitude Intended Simulation Cyclorotation n SJ The imported alignment measurements are shown in red gray in an achromatic image Alignment measurements plotted along with simulations help evaluate a simulation as it is developed by trial and error It is also possible to work on simulations without entering measurements or use the alignment chart to display clinical measurements alone 1999 09 04 54 Orbit 1 8 User s Manual gt Ifyou wish you can print the Alignment Viewer with File Print R You may want to save your own copy of the simulation as it now stands with File Save We have locked the measurement and simulation files we provided so don t worry about inadvertently overwriting them Create a new folder for your simulations Save Orbit 1 8 L50 Palsy Example a Ft 0l Y Date Modified New Folder 4 1997 of 1996 Name of new folder g My Simulations newt Format ort Save this document as Cancel ES If you are working with Orbit demo which disallows saving simply File Quit now if you want a break To resume later without starting over open LS0 Palsy Prep sim 0 1999 09 04 Tutorial DO Simulate an Abnormality with Live Eyes One way to create an abnormality is with the Live Eyes window The imported measurements and in the present case MRI findings suggest left superior oblique
119. osis or treatment 2 compare Orbit s simulated alignment with clinical alignment measurements or desired treatment outcome 3 repeat until you re satisfied with the match A Parameter Fitter helps refine the trial and error process Essentially Orbit clarifies your hypotheses shows you their implications and provides a biomechanical analysis of your ideas It does not replace your judgment and experience in proposing diagnoses and treatments In experimenting with diagnoses you can incorporate whatever you know or suspect perhaps you know that you are dealing with a traumatic superior oblique muscle SO palsy but are unsure of the degree of recovery and of secondary changes in other muscles In experimenting with treatments you can allow for visual status general medical status lifestyle etc You are free to make the tradeoffs your experience suggests Perhaps primary position is most important in one case and reading position in another Orbit s model eyes are biomechanical they are modified by changing properties such as innervations globe dimensions and muscle insertions lengths stiffnesses and contractile forces Thus Orbit is related to the ophthalmotropes of Ruete 1845 Wundt 1862 and others its main advantage being that its behavior is constrained only by knowledge of orbital mechanics and not by the materials and mechanisms feasible in a physical model For each gaze angle Orbit pursues iterative solu
120. out changing longitude or latitude you can rotate the eye about the visual axis If you rotated the eye say 10 about the visual axis red arrow torsion exaggerated its Fick coordinates would be 40 20 10 1999 09 04 40 Orbit 1 8 User s Manual We are also free to rotate the eye using a different coordinate system Imagine the way an astronomical telescope is mounted the telescope is attached to an azimuth disk by a perpendicular axis that carries a pointer Rotating the telescope about the axis points to angle markers drawn on the disk The disk itself is mounted so that it can be tilted up or down about some axis Such a mechanical arrangement follows the Helmholtz system for describing rotation First from some conventional starting position the position that we call straight ahead gaze 0 0 O we elevate the disk by say 40 Second we rotate the azimuth pointer from 0 to 20 and third we twirl the telescope or eye about its visual axis by say 10 We are now at Helmholtz coordinates 40 20 10 This is not the same position as Fick 40 20 10 If you doubt this imagine the rotation 90 90 0 in the two systems Rotational Positions in Orbit Before we can specify a rotational eye position we need to choose a coordinate system and an origin name each coordinate and decide which direction will be positive In Orbit we use the Fick coordinat
121. palsy That s where we ll begin I Select Both Eyes Live Eyes The Live Eyes window will appear You may need to use the scroll bars and size box to center the picture 3 If the Live Eyes do not look like the figure below click Po L and choose the Superior point of view The Live Eyes have 26 regions that produce pop up windows when you click on them the 12 tendons the 12 muscles and the 2 globes ES Click once on the left superior oblique muscle LSO Palsy Preop sim 0 Pov Live Eyes lateral anter lor Super lor Muscle Pulley Location mm from globe center Muscle Pulley Stiffness g mm except O infinite stiffness Relaxed Muscle Length mm without tendon Contractile Muscle Strength of normal Elastic Muscle Strength of normal The muscle Pop up window allows muscle parameters to be modified In a simple SO palsy contractile muscle force is 0 1999 09 04 Orbit 1 8 User s Manual gt To simulate simple SO palsy highlight the Contractile Muscle Strength box change it from 100 to 0 and click __ok_ lateral anter ior super ior Muscle Pulley Location mm from globe center Muscle Pulley Stiffness g mm except O infinite stiffness Relaxed Muscle Length mm without tendon Contractile Muscle Strength of normal Elastic Muscle Strength of normal If the title bar of the Live Eyes window was visible in the background you ma
122. r everything in this folder except for Orbit Prefs holds Point of View settings discussed below If there is no Orbit_POV file Orbit s Point of View window will not show named points of view contains items you may need to put into your System Folder If you are using MacOS 8 0 or 8 1 For System 8 0 amp 8 1 Only Open this folder and drop the contents onto your closed System Folder Let the Finder put the three items contained in their proper places Then restart your computer and launch Orbit again Do not install these items into any system version other than 8 0 or 8 1 1999 09 04 12 Orbit 1 8 User s Manual Adobe Reader 4 0 GA My Simulation Other files and folders in orbit 1 8 contain simulations of strabismic disorders and related files some of which are referred to later in this manual Adobe Reader is needed to read the digital version of this Manual and the Orbit Release Notes We include the 4 0 installation kit on the CD_ROM because earlier versions seem to crash MacOS 8 For the current version of Adobe Reader see www adobe com If Orbit complains that your computer does not have necessary hardware or software then either your MacOS System version is too old remember Orbit has been tested only with MacOS 7 5 5 and later you may be able to upgrade your OS or your computer is inadequate Some old Macs eg MaclIsi may not have math coprocessors and cannot r
123. readsheet program Graphic Eyes are also not printed with File Print Instead use the Write PICTs option in Preferences or Window Settings This will create a PICT file in the 1999 09 04 Orbit Reference 117 folder you choose for the current Graphic Eye if you set the flag in Window Settings or for every Graphic Eye you create if you set it in Preferences PICT format files are viewable with many applications such as SimpleText which came with your Macintosh or with any graphics application that works with PICT files Pop up windows are not printable but the same information can be printed more compactly from the Parameter Editor All the help windows available on the Menu Bar can be printed Some will be paginated in an ugly way sorry Before printing depending on how your Macintosh is set up you may need to use amp Chooser to choose a printer See your Macintosh User s Guide Shortcuts Close Windows in the Background The usual way to close a window in the background is to activate it ie bring it to the foreground and click the close box E or type W Activating a window means waiting for it to update and redraw To avoid the delay hold down the option key and select the window on the Menu Bar eg Both Eyes Close Alignment Chart Quickly Print a Window Wherever you can use File Print you can also use File Print One The d
124. rior oblique palsies Muscle mechanisms revealed by magnetic resonance imaging cty Boca Raton FL pub CRC Press Dyer JA Henderson JW 1958 Orbitonometry in unilateral exophthalmos American Journal of Ophthalmology vol 45 pgs 208 Foster RS 1996 Posterior fixation suture augmetation of vertical muscle transposition surgery Abstr of 22nd AAPOS Mig pgs papers 16 Hotchkiss MG Miller NR Clark AW Green WM 1980 Bilateral Duane s retraction syndrome A clinical pathologic case report Archives of Ophthalmology vol 98 pgs 870 874 Huber A 1970 Duane s retraction syndrome Considerations on pathogenesis and aetiology of the different forms of Duane s retraction syndrome In eds Strabismus 69 pgs 36 43 cty London pub Henry Kympton Koornneef L 1983 Orbital connective tissue In eds Duane TD and Jaeger EA Biomedical Foundations of Ophthalmology cty Philadelphia pub Harper amp Row Chapter 32 Kuhn TS 1970 The Structure of Scientific Revolutions edn 2 cty Chicago pub University of Chicago Press 1999 09 04 152 Orbit 1 8 User s Manual Lockwood 1886 Journal of Anatomy amp Physiology vol 20 isu 1 Miller JM 1985 Applications of the SQUINT computer strabismus model In Association for Research in Vision and Ophthalmology 26 pgs 253 Sarasota FL Investigative Opthalmology and Visual Science Miller JM 1989 Functional anatomy of normal human rectus mu
125. rmless from any damages attributed to their use I may transfer my Orbit license only if the transferee accepts the conditions of this Agreement by returning a signed copy to Eidactics I will not incorporate Orbit in whole or part into another product Print Licensee Name Licensee Title Institution Signature Date Eidactics products are delivered with taxes and postage paid and with a 60 day unconditional satisfaction guarantee Please enclose a purchase order or payment to Eidactics by check or money order drawn on a US bank See our website for the latest software and documentation updates and for related research and reprints provide contact information on next page 1999 09 04 156 Orbit 1 8 User s Manual Eidactics Tell us how to contact you with technical information and where to ship and bill your order Technical Contact First Name Middle Initial o Last Name ___ Degrees Title Shipping Address __ Ship to Technical Contact Otherwise specify First Name Middle Initial Last Name ____ Degrees Title Vox Fax Billing Address __ Bill to Technical Contact __ Bill to Shipping Address Otherwise specify First Name Middle Initial ___ Last Name Degrees Vox Fax 1999 09 04 157 Notes 1999 09 04 158 Orbit 1 8 User s Manual Notes 1999 09 04 159 Notes 1999 09 04 160 Orbit 1 8 User s Manual Notes
126. rting Eye Parameters The eye parameters available in the Expert Level Parameter Editor can also be saved to a text file for use with another application such as a text editor or spreadsheet with Left Eye Export Eye Parameters and Right Eye Export Eye Parameters 1999 09 04 98 Orbit 1 8 User s Manual Parameter Fitter The Parameter Fitter allows Experienced and Expert Users to automatically optimize the fit of an Orbit simulation to a set of clinical measurements by varying selected eye parameters It uses the Nelder Mead Simplex algorithm Press et al 1992 Numerical Recipes in C The Art of Scientific Computing edn 2 Open Both Eyes Parameter Fitter and the Parameter Editor s for the parameters you wish to vary Select each parameter drag across it highlighting the entire field and then drag and drop it into the lower part of the Parameter Fitter window The parameter will expand into a line showing the eye muscle parameter name initial value taken by the fitting procedure minimum and maximum values and the value arrived at by the fitting procedure Eye is L for left eye R for right eye or 3 for third inner eye the Inner Eye is briefly described above in the Test of Binocular Alignment section Mus iS LRZ MR OR TR SO or IO Parameter is the parameter name as in the Parameter Editor possibly abbreviated Initial is the in
127. s to be fibroelastic sleeves consisting of dense bands of collagen and elastin suspended from the orbit and adjacent extraocular muscle sleeves by bands of similar composition Immunohistochemical studies have revealed substantial smooth muscle in the pulley suspensions and in posterior Tenon s fascia The pulleys function as mechanical origins of the recti extraocular muscles in the sense of determining extraocular muscle pulling directions This study was conducted to determine the theoretical effects of the pulleys on the outcome of recti transposition surgery METHODS The functional and anatomical evidence for the existence of the recti extraocular muscle pulleys was reviewed In two patients binocular alignment data were collected using the Hess screen test before and after vertical recti transposition surgeries for lateral rectus paralysis Paths of the recti extraocular muscles were determined using high resolution MRI The Orbit 1 5 extraocular biosimulation program was employed to compute theoretical binocular alignment and muscle paths under alternative conditions including or omitting the pulleys RESULTS Pulleys are required to account for observed paths of recti extraocular muscles following transposition surgery In the absence of pulleys transposition of the superior and inferior recti to the lateral rectus insertion for abducens paralysis would result in bizarre ocular misalignments not observed clinically CONCLUSIONS Th
128. scle Forces 106 Total Longitudinal Muscle Force g 107 Rotational Muscle Force g 108 Unit Moment Vector 109 Rotational Force component g 109 Exporting Mechanical States 111 Point of View 112 Graphic Eyes 113 Other Issues 115 Names 115 Speed 115 Printing 116 Shortcuts 117 Trouble 118 Solutions Could Not Be Found 118 Not Enough Memory 120 Frequently Asked Questions 122 How do the various Preferences and Window Settings differ 122 Where are normal muscle insertion coordinates 123 How do make an Orbit Movie 123 How do Print Orbit Windows 124 When Credit is Due 125 Mathematical Analyses 127 Rotational Force due to Muscle Width 127 Annotated Orbit Bibliography 133 Current Work 133 Overview of Our Research Program 134 Biomechanical Models of Eye Alignment 136 Studies of Eye Muscle Forces Paths amp Pulleys 138 Clinical Application of Biomechanical Modeling 146 Spin Offs 149 Literature Cited 151 Order Form amp License Agreement 155 1999 09 04 viii Orbit 1 8 User s Manual 1999 09 04 Preliminaries 1 Preliminaries What is Orbit The complexity of extraocular muscle coordination has long confused and frustrated students researchers and clinicians Orbit is a unique educational and research tool that provides easy access to a sophisticated biomechanical Orbit 1 8 model able to simulate classical strabismus syndromes and data from individual cases thereby clarif
129. scles Vision Res vol 29 isu 2 pgs 223 40 Miller JM Demer JL 1992 Biomechanical analysis of strabismus Binocular Vision and Eye Muscle Surgery Quarterly vol 7 isu 4 pgs 233 248 Miller JM Demer JL 1999 Clinical Applications Of Computer Models For Strabismus In eds Rosenbaum A and Santiago AP Clinical Strabismus Management pgs 99 114 cty Philadelphia pub W B Saunders Miller JM Demer JL Rosenbaum AL 1990 Two mechanisms of up shoots and down shoots in Duane s syndrome revealed by a new magnetic resonance imaging MRI technique In eds Campos EC Strabismus and Ocular Motility Disorders pgs 229 234 cty London pub Macmillian Press Miller JM Demer JL Rosenbaum AL 1993 Effect of transposition surgery on rectus muscle paths by magnetic resonance imaging Ophthalmology vol 100 isu 4 pgs 475 87 Miller JM Robins D 1987 Extraocular muscle sideslip and orbital geometry in monkeys Vision Res vol 27 isu 3 pgs 381 92 Miller JM Robinson DA 1984 A model of the mechanics of binocular alignment Comput Biomed Res vol 17 isu 5 pgs 436 70 Miller JM Robinson DA Scott AB Robins D 1984 Side slip and the action of extraocular muscles In Association for Research in Vision and Ophthalmology pgs 182 Sarasota FL Investigative Opthalmology and Visual Science Nakagawa T 1965 Topographic anatomical studies on the orbit and its contents Acta Soc Ophthalmol Japan vol
130. t RLat dntint LLatPos Int RLatPos Int R To remind yourself about directions of insertion movement turn on Balloon Help About Balloon Help Show Balloons What is Orbit Not Enough Wiemory Bibliography Ordering Orbit If you insist on knowing An advanced insertion moves along the line of muscle pull at the insertion in such a direction as to stretch the muscle A transposed insertion moves in a direction 90 clockwise from the direction of muscle pull as viewed from outside the eye 1999 09 04 Tutorial 71 I Then click the RSR tendon Fuse Insert Movement around mm from normal basic ES Turn Balloon Help off About Balloon Help Hide Balloons Whatis Orbit Not Enough Memory Bibliography Ordering Orbit Turns Balloon help otf 1999 09 04 72 Orbit 1 8 User s Manual 3s We re ready to do the RSR and RIR transpositions note that we suppose 1 mm of tendon to be lost to the surgery Right eye SRTendon Normal 000 Muse Insert Horement around mm from normal forward Muse Insert Rotation 7 Tendon Length mm Tendon Width mm Musc Insert Movement around imm from normal forward 4 0 Muse Insert Rotation 7 Tendon Length mm Tendon Width mm 1999 09 04 Tutorial 3 The resulting simulated alignment has the same shape as the measurements but the simulatio
131. t modified them yet Therefore the blue circles lie exactly on top of the black crosses obscuring them until we introduce an abnormality R Examine the Alignment Viewer by turning on Balloon Help Help Show Balloons Point to the various buttons and fields to discover what they are for When you are done Help Hide Balloons Click the Window Help Button G2 and read the description of the window There is a more complete discussion of the Alignment Viewer in the Reference section of this manual ZS Enter some identification untitled Alignment Fiewer Fam nmn whiplash O Left Superior Oblique Palsy Doc Gyn nm ate dill Lead Sim Meas raf 4 d2a iss Horm 129917201 Chart type lancaster fick rel Intended Gaze Why do we use intended gaze positions The conventional alternative would be to specify positions of the fixing eye for comparison with the positions of the following eye But then because of the mirror symmetry of the eyes calculating deviations requires interchanging abduction and adduction and reversing the sign of torsion for the fixing eye When you represent deviations graphically as in a Hess Lancaster chart you are using the notion of intended gaze implicitly as we have discussed 1999 09 04 Tutorial 51 Import Alignment Measurements Inside the Orbit 1 8 f folder you will find the L50 Palsy Example folder In
132. teps you should actually perform on your Mac if you wish to follow the presentation 1999 09 04 48 Orbit 1 8 User s Manual Superior Oblique Palsy First we will simulate a composite case of SO palsy in the course of which we will use many basic Orbit functions We will also see some of the strengths and limitations of Orbit and some of the limitations of current methods of measuring binocular alignment We will also confront some gaps in our current understanding of some muscle actions topics for future research Recall that where Orbit cannot confidently perform a calculation it does nothing By leaving such matters to the User Orbit allows hypotheses to be tested Launch Orbit ES Launch Orbit by double clicking on the orbit 1 8 icon The Orbit splash screen appears Thi m i Licensed to is software is l licensed for use on A A mS Phe only one machine Eidactics Visual Biosimulation at a time License Number JMhM 4 30 Orbit is Not Approved for Patient Care Here you see e The Orbit version Is this the version you intended to run e Registration the person identified is responsible for all use made of this licensed software 1999 09 04 Tutorial 49 View the Alignment Pattern If your copy of Orbit is factory fresh all of its Preferences are set to standard factory values A new simulation will open with the help window what Is Orbit and the Alignment View
133. that in each case neither SO palsy alone nor pulley heterotopy alone could account for the observed strabismus patterns CONCLUSION The excyclotorsion of the globe that accompanies SO palsy does not systematically displace all rectus muscles pulleys only the MR pulley and so the MR path is significantly displaced This may be a mechanical consequence of atrophy of the adjacent SO muscle belly Biomechanical modeling suggests that SO disfunction combined with MR pulley heterotopy better accounts for the pattern of binocular misalignment than does either mechanism alone 1999 09 04 140 Orbit 1 8 User s Manual Demer JL Poukens V Miller JM Micevych P 1997 Innervation of extraocular pulley smooth muscle in monkeys and humans Invest Ophthalmol Vis Sci vol 38 isu 9 pgs 1774 1785 PURPOSE Soft pulleys stabilize paths and determine pulling directions of the extraocular muscles EOMs This study was conducted to characterize innervation of smooth muscles SMs supporting these pulleys METHODS Cadaveric human and monkey orbits were step and serially sectioned for histochemical and immunohistochemical staining Before perfusion the superior cervical ganglia of one monkey had been injected with the anterograde tracer Phaseolus vulgaris leukoagglutinin PHA L Immunoperoxidase staining to human SM alpha actin confirmed pulley SM Monoclonal and polyclonal antibodies were used to demonstrate PHA L tyrosine hydrox
134. the secondary deviation of the following left eye would probably be so large as to put the filled red dot on the left off the chart Such subjective alignment measures as were used to collect these data give no indication of whether the fixing eye actually achieved the gaze angle requested or if the subject just approached it as closely as he or she could In the later case the alignment measurements are invalid For this reason we disregard the 5 measurements in the rightmost column for the left eye 1999 09 04 Tutorial 69 ES As before we begin the post op simulation by comparing the final pre op simulation with the post op measurements RLR Palsy PstOp sim 0 LEFT EYE right eye fixing UP FIGHT EYE Cleft ewe fixing OTA HAC eae ao m AB 40 30 40 10 O 10 20 30 40 40 a 40 40 3s0 20 10 10 20 30 40 AB Horizontal Gaze deg longitude 1999 09 04 70 Orbit 1 8 User s Manual We will treat this chronic RLR palsy by transposing the vertical recti Transposition is best performed with the Live Eyes display as the directions involved can be confusing With Live Eyes simply adjust forward and around values until the picture looks right R Open Live Eyes and choose the Right Lateral point of view An RLA Die PstOp sim 1 POY do net ohange Superior Anter ior Infer ior kigh htLateral Foster ior LeftLateral LLat AntSup RLat AntSup LLatPosSup RLatPosSup LLat 4ntin
135. the Parameter Fitter Contractile Muscle Strength of normal 100 00 100 00 100 00 100 00 l untitled eista Parameter Fitter Fit Load Initial _Apply itae ea mm eee mforce_devel_stren mm eee The Help button shows information similar to this Manual section The Settings button opens a window in which you can modify the fitting method Choose the Mean Error Criterion if you want the best overall fit across all gaze positions for which measurements have been entered this might allow a few badly fitted positions Choose the Maximum Error Criterion if you want the worst fitted position to be as good as possible Weights are values from 0 to 10 which determine the relative ie 1 1 1 is the same as 10 10 10 significance of each gaze angle component in the fitting algorithm A weight of 0 means that the component is ignored in calculating the error that is minimized Thus because torsion measurements can be unreliable its weight is set to 0 by default If the torsion component is omitted from a measured gaze point it is of course omitted regardless of the weight 1999 09 04 100 Orbit 1 8 User s Manual It is possible for the Parameter Fitter to try eye parameters that Orbit cannot solve for some gaze angles This may mean parameters are unrealistic measurements are inaccurate or Orbit is flawed You may wish to allow a small number of such Convergence Failures
136. tion on attempted adduction 4 Frequently up shoots or down shoots on adduction We leave this simulation as an exercise for the reader 1999 09 04 82 Orbit 1 8 User s Manual 1999 09 04 Orbit Reference 83 Orbit Reference Here following some general comments on Orbit windows we provide complete descriptions of each Two Types of Windows Does the window have an button If so you must finish your work there and close it before doing anything else Most windows however don t have buttons and it is convenient to leave several of them open on your desktop We leave open Live Eyes or Parameter Editor for trying different lesions and procedures Alignment Viewer to see the overall results and Mechanical State Viewer for corresponding numeric values Orbit windows except the Parameter Fitter know about each other if you make a change eg with the Parameter Editor all dependent windows eg the Alignment Viewer amp Mechanical State Viewer will know that they are out of date For efficiency however we do not update background ie dim windows until they are brought into the foreground To remind you that the values in a background window may not be current inverted and upright question marks are placed around the simulation name If you select an out of date window eg by clicking it to bring it into the foreground it will update and the question marks will disapp
137. tion to Strabismus Models Empirical generalizations Expert systems Homeomorphic models Biomechanical models Physiologic Basis Extraocular imaging Immunohistochemistry and electron microscopy Rectus muscle pulleys Binocular alignment measurements Clinical Applications When Is A Biomechanical Model Useful In Treatment Planning How to Use a Biomechanical Model in Diagnosis Treatment Simulation Role in Teaching and Changing Patterns of Clinical Practice Schools of thought A unifying framework for theory and practice in strabismus Case Studies Heterotopic pulleys amp pattern strabismus Vertical rectus transposition with posterior augmentation sutures Summary And Prospects Bibliography Miller JM Demer JL 1997 New Orbital Constraints on Eye Rotation In eds Fetter M Misslisch H and Tweed D Three dimensional kinematic principles of eye head and limb movement cty Chur Switzerland pub Harwood The familiar notion that extraocular muscle paths are little constrained except at origins and insertions was called into question by biomechanical modeling Miller and Demer 1992 Magnetic resonance imaging having previously shown that the paths of rectus muscle bellies remain fixed in the orbit during large ocular rotations Miller 1989 was then used to show that they remained fixed across large surgical transpositions of their insertions Miller et al 1993 confirming that pulleys near the globe equator couple muscle paths t
138. tions involving extraocular connective tissues and the innervations paths and tensions of all muscles in both eyes according to equations given in part by Robinson 1975 and Miller and Robinson 1984 Orbit is a Macintosh computer program and has been designed to operate in the consistent natural way typical of Macintosh programs 1999 09 04 Preliminaries Concerning Medical Use Though based on the best data and analyses available Orbit is not approved for and should not be relied on for decisions about patient care Orbit is not intended to substitute for any established diagnostic or treatment planning procedure First we are only beginning to understand extraocular muscle cooperation in terms compatible with the physical sciences that is on a biomechanical level The field is just emerging from the schools of thought stage where knowledge and practice are organized around prominent teachers but little is understood in terms of generally accepted first principles Kuhn 1970 Second orbital and brain physiology of a particular patient may differ from the normal population values in the model Finally Orbit has not been widely tested against actual patient data What is Orbit Not There are two other fundamentally different types of models that have been used in strabismus analysis empirical generalizations and expert systems Orbit contains no pre programmed demonstrations o
139. type lancaster fick rel A LEFT EYE fright eye fixing UF RIGHT EYE Cleft ewe fixing 40 IJ E E t G q z 2 d E J rt eo OM AB 40 SO 2O 10 O 10 20 30 40 40 4O0 40 30 20 10 0 10 20 30 40 AB Intended Horizontal Gaze deg longitude Simulation _ Cyelorotation amp 3 Alignment Chart Below the information fields is a Hess Lancaster type alignment chart The orientation of the chart follows clinical convention with positions of the following ie moving under cover left eye on the left and that of the following right eye on the right Each intended gaze position is represented as a small black cross The intended gaze position of a following eye is the position it would assume if the 1999 09 04 Orbit Reference 93 whole system were normal Equivalently it is the position of the fixing eye with the signs of horizontal and torsional gaze components reversed because of the eyes mirror symmetry The set of intended gaze positions for each eye can be selected from pop up lists above the alignment charts Ls fone Primary Position Ht30 415 WtS0 415 Ht30 415 W430 415 ne Ht40 420 Vt4do a20 Ht40 420 VWtdo 420 ne Ht40 4107 Ween 410 H 40 45 y 0 H 0 W407 a5 He40 a5 Yao amp H 0 W40 A5 Positions of the following eye are shown as blue circles o with connecting lines to emphasi
140. uction elevation and extorsion abduct or abduction is the 1st Fick coordinate rotation away from primary position Positive rotation about this vertical axis moves the visual axis away from the body s midline along the equator elevate or elevation is the 2nd Fick coordinate rotation It is rotation in the plane of the local longitude see globe figure above Positive rotation about this horizontal axis moves the visual axis up along a longitude line extort or extorsion is the 3rd Fick coordinate rotation It is rotation about the visual axis such that the top of the eye moves laterally Deviations It is useful to speak of a fixing eye and a following eye In some alignment tests the following eye is actually covered and so is referred to as the covered eye and the patient voluntarily moves the fixing eye to various standard gazes In other tests neither eye is covered but it is arranged that there is nothing visible to both eyes that is that there is no fusional target The position of the following eye is ascertained as the patient fixates standard gaze targets Deviations are differences between following eye and fixing eye rotational positions One might more descriptively and less humorously call them misalignments but deviations is conventional exo dev or exodeviation following eye abduction fixing eye abduction The appears because of the mirror symmetry of the e
141. ulated left eye matches the measurements in showing limited depression especially in adduction and a V pattern The tilt of the arrows which indicates torsion shows that simulated cyclorotation depends on vertical gaze whereas measured cyclorotation is less orderly Itis not unusual to find that measurements of cyclorotation do not match simulations this may be because clinical measurements are often unreliable Miller and Demer 1999 In any case note that the tilt of cyclorotation arrows in the Alignment Viewer is multiplied by 5 for visibility so that most of these discrepancies are small Expected secondary deviations are seen in the simulated following right eye and these also match the clinical data 1999 09 04 58 Orbit 1 8 User s Manual The remaining systematic differences are that the simulation shows greater eso and left hypophorias compared to the measurements Regarding the left hypophoria we suppose that as a consequence of the chronically elevated posture of the left eye the LSR has shortened by 2 mm from 32 4 to 30 4 The small residual horizontal difference between simulation and measurement is nulled by shortening LLR by 0 7 mm from 36 2 to 35 5 and lengthening LMR by 0 7 mm from 31 0 to 31 7 We have saved this simulation as LSO Palsy PreOp sim 2 LSO Palsy Preop sim 2 Alignment fiewer Fam nm or lash Left Saas Oblique Palsy Doc Gwn nm wallace Pre Op Saas
142. un Orbit As you work with Orbit you will create new simulation files the generic Macintosh term for which is documents you may put these anywhere Orbit Demo does not allow simulations to be saved Cleaning Up gt The archive file or files Orbit 1 8 sea you may have are no longer needed Drag them to the Trash to complete the installation If the various Orbit files do not have their icons shown below or if double clicking an Orbit simulation fails to open it with Orbit you must rebuild your Macintosh desktop To do this restart your Mac while holding down the Command and Option keys Sharing Orbit with your Colleagues As an Orbit licensee you are free to share Orbit with your colleagues within the terms of your License Agreement 1999 09 04 Preliminaries 13 Each license allows one simultaneous use of Orbit This means that you may install and register Orbit on several machines eg an office and a home computer or on a single machine for use by several people provided that all installations are under your control in that you can ensure that only one copy is in use at any time You may also distribute copies of Orbit that will not be under your control but in this case you must not share your registration key or the Orbit file see below that contains an encrypted key that you previously entered Your registration key is the 10 letter code shown on the last line of
143. uscles pass through pulleys located posterior to the equator and elastically coupled to the orbital wall Soft rectus muscle pulleys are a recent discovery and since one might reasonably be skeptical about claims of new functionally significant eross anatomic structures in such a familiar part of the body we will review the findings Prior to the development of computational models of extraocular biomechanics it seemed sufficient to describe extraocular anatomy in terms of origins insertions and cross sections of extraocular muscles measured in cadavers But then several new results appeared 1 Modeling The attempt to calculate binocular alignment from first principles Robinson 1975 Miller and Robinson 1984 Miller et al 1984 made it obvious that paths of EOMs and gaze dependence of their paths could not be inferred from cadaveric data but had to be measured in alert subjects 1999 09 04 A Biomechanical Approach 29 2 Imaging These measurements were performed in monkeys and humans by Miller et al 1984 Simonsz et al 1985 Miller and Robins 1987 and Miller 1989 The main finding of all these studies was that rectus muscle bellies are remarkably stable with respect to the orbital wall over the full range of gaze A Mec y A A j y l AES an ce me as E P ee A as DNAD DN DNAB 1999 09 04 30 Orbit 1 8 User s Manual 3 More modeling We consider two
144. vation azimuth and torsion Although the same term is used to describe the third coordinate in both systems Fick and Helmholtz torsion are only qualitatively similar they both describe rotation about a visual axis the direction of which is determined by the first two coordinates But because the first two coordinates are different except in some special cases torsion values describing the same rotation are different as well 1999 09 04 A Biomechanical Approach 39 Orbit uses Fick rotational coordinates You may already be familiar with Fick coordinates as the longitude and latitude lines conventionally drawn on a globe of the earth Imagine the eye at the center of the globe and its visual axis pointing at the intersection of 0 longitude and 0 latitude green arrow First rotate the eye so that the visual axis moves along the equator until it points to say 40 longitude yellow arrow Second rotate the eye so that the visual axis moves straight up the 40 longitude line until it points to the 20 latitude line orange arrow The longitude latitude coordinates of the eye are by definition now 40 20 Notice that the elongated dimension of the arrow which was parallel to the local longitude line at 0 0 O and at 40 0 O remains parallel at 40 20 0 This means that torsion in the Fick system is zero Of course one more independent dimension of rotation remains with
145. ver if you are concerned that strabismology in its current form may not be equal to coming technical economic and competitive demands you should waste no time in adding this new tool to your armamentarium So far as we know biomechanical modeling offers the only coherent scientific approach to problems of eye alignment 1999 09 04 Preliminaries 5 Conventions Used in this Manual We will refer to items from the Menu Bar at the top of the Macintosh screen with the symbol For example File New means move the cursor to the File item on the Menu Bar then click and drag to select New amp About Orbit means move the cursor to the item on the Menu Bar then click and drag to select About Orbit In the Tutorial section of the manual we use a pointing finger I to indicate actions you should take to follow the example on your Macintosh The digital graphics in this Manual are in color although printed copies are grayscale for reasons of cost Color PDF Portable Document Format files are provided on the Orbit CD ROM see below and on our Website at www eidactics com Software Web editions will be updated as indicated by fractional edition numbers eg 1 1 PDF files can be viewed and printed with Adobe Acrobat Reader provided on the Orbit CD ROM and also available online at www adobe com 1999 09 04 Orbit 1 8 User s Manual We Did Not Do This Alone
146. ver 1 mm seems a bit small Should you wish to pursue this simulation further you might advance to Expert Level which allows you to modify Globe Translational Stiffness We think it reasonable to guess that a chronic co contractive syndrome would soften the encapsulated fat pads that control globe translation Reducing Globe Translational Stiffness greatly increases the magnitudes of retraction and protrusion Type 2 The signs of Duane s Type 2 are 1 Normal or slightly limited abduction 2 Limited or absent adduction 3 Globe retraction on attempted adduction 4 Frequently up shoots or down shoots on adduction Our theory is that abducens innervation of LR is normal sign 1 but that the MR branch of the oculomotor nucleus is providing partial innervation of LR signs 2 3 and 4 One change to the Connection Matrix 1999 09 04 Tutorial 81 Brain y Motor Hucleus Connection Weights of nuclei s total excitation Abducens 1000 T T T T OculoesMR 100 T 0 T Oeulo SR 0 100 oO T Deulo IF oO T 100 T Trochlear J J J 100 Oeulo 10 E 0 E 0 10 UF RIGHT EYE Cleft eye fixing mom O moomoo o results in the following Alignment LJ Chart E t G qa z d J l a t DH 40 40 s0 20 10 0 10 20 30 40 AB Horizontal Gaze deg longitude Type 3 Duane s Type 3 is characterized by 1 Limited or absent abduction 2 Limited or absent adduction 3 Globe retrac
147. wing terms Extorsion as we have explained is simply the third coordinate of 3 D rotation with a hint about the positive direction Excyclo Dev or excyclodeviation intrinsically involves two eyes Certain clinical tests of binocular eye alignment such as the Lancaster test yield a value that is the difference between torsions in the fixing and following eyes That is with normal retinal correspondence the patient may place his red streak at an angle to the examiner s green streak either because his following eye has abnormal torsion the usual possibly mistaken presumption his fixing eye has abnormal torsion or both Such alignment tests measure the difference between fixing and following eye torsions There is no conventional term to specify this difference so by analogy with exodeviation and hyperdeviation which refer to horizontal and vertical misalignment of the following eye relative to the fixing eye we coin the terms cyclodeviation and excyclodeviation and the abbreviation excyclo dev to refer to torsional misalignment of the following eye relative to the fixing eye To summarize Torsion extort is rotation about the visual axis Listing Torsion listing is normal torsion according to Listing s law 1999 09 04 44 Orbit 1 8 User s Manual Cyclorotation excyclo extort listing Cyclodeviation excyclo dev following eye extort fixing eye extort where the
148. ximum pure red muscle color saturation 1999 09 04 114 Orbit 1 8 User s Manual If you wish to save Graphic Eyes pictures to disk eg for printing check MWrite PICTs PICT files are graphics files readable by most graphics applications Press to determine where the files will be saved i Beautify increases the resolution of the pictures which consequently take longer to draw Having checked Write PICTs each time you create or alter a Graphic Eyes window a PICT file will be written to the chosen folder its name derived from the Graphic Eyes window title bar Remember to uncheck Write PICTs when you re done saving PICTs since otherwise unwanted files will accumulate Click Set From Sim Prefs to adopt as current window settings the values ihre in Both Eyes Preferences for Sim Click _aK_ to apply yo oly your choices to the current Live Eyes window or faneet to forget them 1999 09 04 Orbit Reference 115 Other Issues Names The title bar of most Orbit windows gives the name of the simulation eg untitled If the window pertains to a particular intended gaze position it too is shown in the title bar eg untitled 0 0 Speed Hardware The hardware on which you run Orbit is the most important determinant of speed For comparison we ran a simulation with normal eyes and all 289 gaze angles for one eye All calculations shown in the flowchart shown in the secti
149. xing and Following Eyes 18 Muscle Force Model 19 Elastic Force stiff vs soft 20 Contractile Force strong vs weak 21 Secondary Effects of Surgery 22 Manipulating the Muscle Model 23 Basic Data and Operations 26 Rectus Muscle Pulleys 28 Again 33 What is a Simulation 34 Test of Binocular Alignment 35 1999 09 04 vi Orbit 1 8 User s Manual Eye Position 37 Coordinates for Translation 37 Coordinates for Rotation 38 Rotational Positions in Orbit 40 Deviations 41 Torsion Of Course Depends on the Coordinate System 42 Extorsion Excyclo Excyclo Dev 43 Limitations of Orbit 44 Tutorial Examples 47 Superior Oblique Palsy 48 Launch Orbit 48 View the Alignment Pattern 49 Intended Gaze 50 Import Alignment Measurements 51 Simulate an Abnormality with Live Eyes 55 Plan a Treatment 59 Avoid a Poor Treatment 60 Plan a Treatment continued 62 Lateral Rectus Palsy 65 Duane s Retraction Syndrome 77 Type 1 78 Type 2 80 Type 3 81 Orbit Reference 83 Two Types of Windows 83 Preferences 84 Intended Gaze Selector 90 Alignment Viewer 92 Info Fields 92 Alignment Chart 92 Window Settings amp Help 93 Deviation Chart amp Notes Box 94 Live Eyes 95 Parameter Editor 97 Exporting Eye Parameters 97 Parameter Fitter 98 Measured Gaze Editor 102 Importing Clinical Measurements 103 Exporting Measurements amp Simulated positions 105 1999 09 04 Contents vii Mechanical State Viewer 106 Mu
150. y have noticed that inverted and upright question marks 3 appeared around the simulation name when you altered Contractile Muscle Strength in the pop up window Similarly the Alignment Viewer shows the question marks now oy L50 Palsy Preop sim 0 I Click on the Alignment Viewer or select Both Eyes Alignment Viewer Notice that the question marks disappear when the Alignment Viewer comes into the foreground The question marks indicate that the window is not up to date For efficiency we only update windows when they are brought into the foreground eg by clicking them Windows in the background which are always dim may therefore not reflect changes you have recently made and the question marks appear to remind you of this 1999 09 04 Tutorial 37 We have saved this stage of the simulation as LSO Palsy PreOp sim 1 LSO Palsy Preop sim 1 Alignment Fiewer Fam nmn whiplash Left Superior Oblique Palsy Doc Gyn nm pe ee Sim Meas ral 4 d 23193 Horm 12990531 Chart type lancaster Tick rel Lz LEFT EYE right eye fixing LIP RIGHT EYE Cleft eve fixing 40 20 lJ p t E a z d J Tat Ea OM AB 40 230 20 10 10 20 30 40 40 4O 40 30 40 10 0 10 240 30 40 AB Intended Horizontal Gaze deg longitude Simulation Cyclorotation 51 With just one parameter change the simulation is already fairly good The sim
151. yes Exodeviation is positive when the following eye is more abducted than fixing eye is adducted 1999 09 04 42 Orbit 1 8 User s Manual hyper dev or hyperdeviation following eye elevation fixing eye elevation Hyperdeviation is positive when the following eye is more elevated than fixing eye excyclo dev or excyclodeviation following eye extorsion fixing eye extorsion The appears because of the mirror symmetry of the eyes Excyclodeviation is positive when the following eye is more excyclorotated than the fixing eye is incyclorotated Torsion Of Course Depends on the Coordinate System Torsion as we have explained is the third coordinate of 3 D rotation What is normal or physiologic torsion We have seen that 3 independent component rotations or 3 degrees of freedom are available for 3 D rotations Donder s Law states that the eye position control system uses only two degrees of freedom torsion is not independently controlled and for each gaze the normal eye always assumes some particular torsion Listing s Law tells what that unique torsion value is that is Listing s Law gives a torsion value for each pair of numbers specifying gaze We should not now be surprised that the value of this normal or Listing torsion depends on the coordinate system we use Because of the way a normal eye or at least one that obeys Listing s Law rotates it tur
152. ying diagnostic and treatment possibilities in well defined physiologic terms Orbit is used all over the world e Ophthalmologists Optometrists and Orthoptists use Orbit to model complex cyclo vertical and innervational disorders refining diagnostic and treatment planning skills e Researchers in vision and oculomotility use it to study orbital mechanics in humans and non human primates for instance to distinguish orbital from central determinants of oculomotor phenomena e Teachers supplement the ophthalmology curriculum with self paced strabismus simulation laboratories e Students working with Orbit are better able to consolidate loosely connected facts and observations into a solid sense of how the extraocular muscles work Orbit is a tool for analysis of extraocular mechanical and innervational factors in eye alignment It contains a pair of model eyes you can modify to reflect supposed causes of motility disorders and proposed treatments and a simulated eye alignment test which shows how the modified eyes behave Orbit is used to create models of extraocular disorders and treatments observe their effects on eye alignment and understand the reasons for those effects in well defined biomechanical terms 1999 09 04 Orbit 1 8 User s Manual Mac Orbit is used in a trial and error mode Beginning with a pair of simulated normal eyes you 1 alter one or both to reflect your ideas about diagn
153. ylase dopamine beta hydroxylase phenylethanolamine N methyltransferase neuronal nitric oxide synthase NOS and synaptophysin The NADPH diaphorase reaction was also used as a marker for NOS and the acetylcholinesterase AChE reaction for acetylcholine RESULTS Pulleys consisting of collagen and elastin sleeves supported by connective tissue containing SM were observed around rectus muscles of humans and monkeys The human and monkey SM was richly innervated Axons terminating in motor end plates within SM bundles were immunoreactive to PHA L tyrosine hydroxylase and dopamine beta hydroxylase but not phenylethanolamine N methyltransferase indicating innervation of pulley SM from the superior cervical ganglion by projections using norepinephrine Smaller axons and motor end plates were also demonstrated in SM using NADPH diaphorase and NOS immunoreactivity indicating nitroxidergic innervation and using AchE indicating cholinergic parasympathetic innervation The pterygopalatine and to a lesser extent the ciliary ganglia but not the Edinger Westphal nucleus contained cells immunoreactive to NOS suggesting that nitroxidergic innervation to pulley SM is mainly from the pterygopalatine ganglion CONCLUSIONS The SM suspensions of human and monkey EOM pulleys are similar and receive rich innervation involving multiple neurotransmitters These complex projections suggest excitatory and inhibitory control of EOM pulley SM and support
154. your Registration Information Card pictured a few pages back You may Loan your distribution media CD ROM floppy disks or downloaded archive but not your Registration Information Card which may have been included with the distribution media Copy all the files from the folder orbit 1 8 except for D3 the file orbitPrefs Orbit_Prefs stores the registration information you entered from your Registration Card as described above Distributing it would violate your license agreement Download the latest version of Orbit from our Website www eidactics com Software Such shared and downloaded copies are fully functional except that output functions are disabled To enable output functions for a new independent user a new Orbit License must be purchased Please be mindful of the difficulty maintaining software as complex as Orbit for our small specialized market By honoring your license agreement you help make possible ongoing development and maintenance of Orbit 1999 09 04 14 Orbit 1 8 User s Manual Click for Help Helpful information embedded in a program is particularly useful it is there when you need it and can be context sensitive you don t have to search for the topic you re having a problem with because the program knows where you are Orbit provides three kinds of help Window Help Buttons Many Orbit windows contain a help button Click it for a description of the window
155. ze Editor Eye Rotation abduct 7 7 0 elevate 31 5 exicyd lo rot The Expert Level Measured Gaze Editor also contains fields for eye translation in the unlikely event that they are actually measured 1999 09 04 Orbit Reference 103 Importing Clinical Measurements Many clinicians enter alignment measurements into spreadsheet or database programs Most such programs can write their data as tab separated text or some similar file format intended for export to other programs Orbit can read most such files directly Each line in an imported file can contain the following values in order separated by tabs spaces or commas intended abduction deg intended elevation deg measured abduction deg measured elevation deg measured excyclorotation deg measured sideways globe translation mm measured protruding globe translation mm measured upward globe translation nm The first two fields identify each line by horizontal and vertical intended gaze positions the remaining values are optional If a value is unavailable use 999 as a placeholder It s also OK to have short lines which omit trailing values eg globe translation and extorsion are rarely measured so the last 3 values will usually be omitted So that it can read files that contain other text besides the data Orbit ignores lines beginning with the following three characters gt so these characters can be used
156. ze the pattern An arrow through each circle shows cyclorotation torsion in excess of normal Listing s Law torsion as tilt from straight up multiplied by 5 for visibility Any clinical alignment measurements you have entered are shown as red circles o with red connecting lines All angles are in degrees Window Settings amp Help At the top of the window are a window settings button wa and a window help button GREE The window help button you will recall provides the present description Pressing RE Alignment Chart Simulation Measurements Deviation Chart je Simulation Measurements Intended Gazes Show gaze angle differences in prism diopters Da Here we ve chosen both simulation results and clinical measurements to appear in the alignment chart as shown above 1999 09 04 94 Orbit 1 8 User s Manual We have also chosen to show deviations from intended gazes of the simulation results for 30 intended gazes primary position is always shown as well To apply these settings and return to the Alignment Viewer press _ok_ The new settings are temporary in that they are associated with the current instance of the Alignment Viewer window if you close and then reopen the Alignment Viewer settings will revert to those given in Both Eyes Preferences for Sim Clicking has the same effect Press to undo any changes

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