Clinical Orthoptics - Startseite › download › 0000 › 5954 › ...normative data. Section II...

ISBN 978-1-4443-3934-5

5439334441879

ORTHOPTICSFiona J. Rowe

THIRD EDITION

Clinical

Clinical O

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Clinical ORTHOPTICSFiona J. RoweTHIRD EDITION

Clinical Orthoptics has become established as a leading textbook providing fundamental

information on anatomy, innervation and orthoptic investigation, in addition to diagnosis and

management of strabismus, ocular motility and related disturbances. It is a valuable resource

for trainee ophthalmologists as well as orthoptic and optometry students. Qualified orthoptists,

general ophthalmologists and optometrists will also find helpful guidance in these pages.

In this third edition, the author has maintained the goal of producing a user-friendly, clinically

relevant and succinct book, while revising it to reflect a variety of developments in the field.

KEY FEATURES

M Essential reading for students of orthoptics, optometry and ophthalmolology

M Now fully revised and updated

M Generously illustrated with photographs and line drawings

M Includes diagnostic aids, case reports and helpful glossary

ABOUT THE AUTHOR

Fiona J. Rowe is a Senior Lecturer in Orthoptics at the University of Liverpool, and lectures extensively to undergraduate and postgraduate orthoptists, trainee and qualified ophthal-mologists, ophthalmic nurses and other members of the multi-disciplinary eye care team.

RELATED TITLESNormal Binocular Vision:Theory, Investigation and Practical AspectsDavid Stidwill and Robert FletcherISBN: 978-1-4051-9250-7

Diagnosis and Management of Ocular Motility DisordersThird EditionAlec M. Ansons and Helen DavisISBN: 978-0-632-04798-7

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Clinical Orthoptics

i


Dedication

This book is dedicated to my family

ii


Clinical Orthoptics

Third Edition

Fiona J. RowePhD, DBO, CGLI CertEd

Senior Lecturer, Directorate of Orthoptics and Vision Science,University of Liverpool, Liverpool, UK

A John Wiley & Sons, Ltd., Publication

iii


This edition first published 2012C© 1997, 2004 by Blackwell Publishing LtdC© 2012 by Wiley-Blackwell

Wiley-Blackwell is an imprint of John Wiley & Sons, formed by the merger of Wiley’s global Scientific,Technical and Medical business with Blackwell Publishing.

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First edition published 1997 by Blackwell ScienceSecond edition published 2004 by Blackwell Publishing LtdThird edition published 2012 by Wiley-Blackwell

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Library of Congress Cataloging-in-Publication Data

Rowe, Fiona J.Clinical orthoptics / Fiona J. Rowe.—3rd ed.

p. ; cm.Includes bibliographical references and index.ISBN 978-1-4443-3934-5 (pbk. : alk. paper)I. Title.[DNLM: 1. Ocular Motility Disorders–Outlines. 2. Craniosynostoses–Outlines.

3. Orthoptics–methods–Outlines. 4. Strabismus–Outlines. WW 18.2]617.7’62–dc23

2011037444

A catalogue record for this book is available from the British Library.

Set in 10/12.5pt Sabon by Aptara R© Inc., New Delhi, India

1 2012

iv

http://www.wiley.com/wiley-blackwell


Contents

Preface xiAcknowledgements xiiList of Figures xiiiList of Tables xvii

SECTION I 1

1 Extraocular Muscle Anatomy and Innervation 3Muscle pulleys 3Ocular muscles 5Innervation 10Associated cranial nerves 12References 15Further reading 16

2 Binocular Single Vision 17Worth’s classification 17Development 17Retinal correspondence 19Physiology of stereopsis 20Fusion 23Retinal rivalry 24Suppression 24Diplopia 25References 27Further reading 28

3 Ocular Motility 29Saccadic system 29Smooth pursuit system 31Vergence system 33Vestibular-ocular response and optokinetic response 35Brainstem control 37Muscle sequelae 39Past-pointing 40Bell’s phenomenon 41References 41Further reading 43


vi Contents

4 Orthoptic Investigative Procedures 45Visual acuity 45Cover test 60Ocular motility 64Accommodation and convergence 68Retinal correspondence 73Fusion 77Stereopsis 82Suppression 89Synoptophore 91Aniseikonia 97Fixation 98Measurement of deviations 99Hess charts 105Field of binocular single vision 108Uniocular field of vision 110Measurement of torsion 111Parks-Helveston three-step test 113Diplopia charts 113Bielchowsky phenomenon (dark wedge test) 115Forced duction test 115Forced generation test 115Orthoptic exercises 115References 119Further reading 124

SECTION II 129

5 Heterophoria 131Classification 131Aetiology 131Causes of decompensation 132Esophoria 132Exophoria 132Hyperphoria/hypophoria 133Alternating hyperphoria 133Alternating hypophoria 133Cyclophoria 133Incomitant heterophoria 133Hemifield slide 133Investigation of heterophoria 134Management 135References 136Further reading 137

6 Heterotropia 138Esotropia 138Factors necessary for development of binocular single vision 139Constant esotropia with an accommodative element 140Constant esotropia without an accommodative element 141Accommodative esotropia 146


Contents vii

Relating to fixation distance 151Exotropia 155Hypertropia 168Hypotropia 168Cyclotropia 169Dissociated vertical deviation 170Dissociated horizontal deviation 172Quality of life 173Pseudostrabismus 174References 175Further reading 184

7 Microtropia 189Terminology 189Classification 190Investigation 191Management 194References 194Further reading 195

8 Amblyopia and Visual Impairment 197Classification 197Aetiology 197Investigation 198Management 199Eccentric fixation 205Cerebral visual impairment 205Delayed visual maturation 206PHACE syndrome 207References 207Further reading 212

9 Aphakia 215Methods of correction 215Investigation 215Problems with unilateral aphakia 216Management 216References 218Further reading 219

SECTION III 221

10 Incomitant Strabismus 223Aetiology 223Aid to diagnosis 225Diplopia 226Abnormal head posture 227References 230Further reading 231

11 A and V Patterns 232Classification 232Aetiology 232


viii Contents

Investigation 236Management 238References 241Further reading 243

12 Accommodation and Convergence Disorders 245Accommodative disorders 245Presbyopia – physiological 245Presbyopia – premature (non-physiological) 246Accommodative insufficiency 247Accommodative fatigue 248Accommodative paralysis 248Accommodative spasm 249Accommodative inertia 250Micropsia 251Macropsia 251Convergence anomalies 251Convergence insufficiency 252Convergence paralysis 254Convergence spasm 254Specific learning difficulty 254References 255Further reading 257

13 Ptosis and Pupils 259Ptosis 259Marcus Gunn jaw-winking syndrome 263Lid retraction 264Pupils 264References 269Further reading 271

14 Neurogenic Disorders 272III (third) cranial nerve 272IV (fourth) cranial nerve 280VI (sixth) cranial nerve 288Multiple sclerosis 292Acquired motor fusion deficiency 293Non-accidental injury 294Premature visual impairment 295Ophthalmoplegia 296References 300Further reading 307

15 Mechanical Paralytic Strabismus 310Congenital cranial dysinnervation disorders 312Brown’s syndrome 319Adherence syndrome 324Moebius syndrome 325Strabismus fixus syndrome 327Thyroid eye disease 327


Contents ix

Orbital injuries 333Blow-out fracture 334Soft tissue injury 339Supraorbital fracture 341Naso-orbital fracture 341Zygoma fracture 341Conjunctival shortening syndrome 342Retinal detachment 342Cataract 343Macular translocation surgery 344References 344Further reading 350

16 Myogenic Disorders 354Thyroid eye disease 354Chronic progressive external ophthalmoplegia 354Myasthenia gravis 355Myotonic dystrophy 358Ocular myositis 358Kearns–Sayre ophthalmoplegia 359References 359Further reading 361

17 Craniofacial Synostoses 362Plagiocephaly 362Brachycephaly 362Scaphocephaly/dolichocephaly 362Occipital plagiocephaly 362Apert’s syndrome 363Craniofrontonasal dysplasia 363Crouzon’s syndrome 363Pfeiffer syndrome 363Saethre–Chotzen syndrome 364Unicoronal syndrome 364General signs and symptoms 364Ocular signs and symptoms 365Management 365References 366Further reading 367

18 Nystagmus 368Aetiology 368Classification 368Investigation 373Management 375References 378Further reading 380

19 Supranuclear and Internuclear Disorders 382Saccadic movement disorders 382Smooth pursuit movement disorders 384


x Contents

Vergence movement disorders 385Gaze palsy 386Optokinetic movement disorders 394Vestibular movement disorders 395Brainstem syndromes 395Skew deviation 397Ocular tilt reaction 398Ocular investigation 398Management options 400References 401Further reading 405

SECTION IV Appendices 407

Diagnostic Aids 409

Abbreviations of Orthoptic Terms 418

Diagrammatic Recording of Ocular Motility 424

Diagrammatic Recording of Nystagmus 426

Glossary 428

Case Reports 441

Index 459

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Preface

Clinical Orthoptics has become established as a basic reference text providingfundamental information on anatomy, innervations and orthoptic investigation,plus diagnosis and management of strabismus, ocular motility and related visualdisturbances. As with previous editions, the third edition is not designed to providein-depth discussion of the content as it is recognised that this can be found in otherexcellent texts, in systematic reviews and in journal literature.

Following the revision of previous editions, this third edition, in addition to manyof the original illustrations, contains new figures, tables and flowcharts designed toenhance the written text. Reference and further reading lists for each chapter havebeen extended and include up-to-date literature.

The layout of the text remains similar to that of the previous edition. Section Iconcentrates on anatomy and innervations of extraocular muscles including musclepulley systems and associated cranial nerves. Ocular motility and orthoptic inves-tigative techniques have been updated to include new assessments and reference tonormative data. Section II refers to concomitant strabismus and Section III to in-comitant strabismus. There has been considerable revision to add new informationon conditions not previously included. A new chapter on craniofacial synostosissyndromes has been added. Section IV includes an updated list of abbreviationsand glossary of definitions with additions to the information provided on diagnos-tic aids, flowcharts and illustrative case reports.

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Acknowledgements

Thanks are due to my colleagues and undergraduate students at the University ofLiverpool, whose discussions provoke enquiry and understanding of orthoptics.Thanks are due to Addenbrooke’s Hospital, Cambridge, for permission to use pa-tient photographs and to the patients and parents for their consent to use theseimages. The glossary incorporates terminology from the British and Irish OrthopticSociety, and thanks are due to the Society for permission to use the glossary ter-minology. Finally, a thank you to the team at Wiley-Blackwell, the publisher, fortheir input to this text.

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List of Figures

1.1 Orbital apex 41.2 Extraocular muscles 41.3 Medial rectus action 51.4 Lateral rectus action 61.5 Superior rectus action 71.6 Inferior rectus action 71.7 Superior oblique action 81.8 Inferior oblique action 91.9 Extraocular muscle insertions 91.10 Cardinal positions of gaze – position of main action of

extraocular muscles9

2.1 Projection in normal retinal correspondence 202.2 Projection in abnormal retinal correspondence 202.3 Projection in heteronymous diplopia 212.4 Projection in homonymous diplopia 222.5 Horopter 232.6 Right convergent strabismus with suppression 252.7 Right convergent strabismus with pathological diplopia 262.8 Right convergent strabismus with paradoxical diplopia 263.1 Saccadic eye movement control pathways 323.2 Smooth pursuit eye movement control pathways 343.3 Vergence eye movement control pathways 353.4 Vestibulo-ocular and optokinetic response control pathways 363.5 Sagittal cross section of brainstem; schematic representation 373.6 Coronal cross section of brainstem; schematic representation 383.7 Sagittal view of cortical areas; schematic representation 394.1 Optics of visual acuity 464.2 Forced choice preferential looking 474.3 Teller cards 484.4 LogMAR test 484.5 LEA symbols 494.6 Snellen test 504.7 Sheridan Gardiner test 514.8 Kay’s pictures 514.9 Cardiff acuity cards 52


xiv List of Figures

4.10 Vistech chart 554.11 LEA contrast numbers 554.12 Heidi contrast faces 564.13 Hypermetropia 574.14 Myopia 574.15 Astigmatism 584.16 Occluders 604.17 Fixation targets 614.18 Cover/uncover test in manifest strabismus 624.19 Cover/uncover test in latent strabismus 634.20 Alternate cover test 634.21 Rotation of the eye 654.22 Optokinetic nystagmus Drum 674.23 RAF rule 694.24 Flipper lenses 704.25 Bagolini glasses 744.26 Results with Bagolini glasses 744.27 Worth’s four lights test 754.28 Risley prism (a): Prism bars and loose prisms (b) 794.29 Response to overcome a base out prism 794.30 Lang two pencil test 844.31 Frisby stereotest 844.32 FD2 stereotest 854.33 Lang stereotest 864.34 TNO stereotest 874.35 Titmus/Wirt stereotest 884.36 Randot stereotest 884.37 Sbisa bar 894.38 Amsler chart 914.39 Synoptophore 924.40 Optics of the synoptophore 924.41 Maddox slides 934.42 Simultaneous perception slides 944.43 Fusion slides 954.44 Stereopsis slides: (a) gross stereopsis; (b) detailed stereopsis 964.45 Angle kappa 964.46 Angle kappa slide assessment 974.47 Fixation 984.48 Fusion response with 4 dioptre prism test 994.49 Suppression scotoma response with 4 dioptre prism test 994.50 Prism position 1014.51 Hirschberg’s corneal reflections 1034.52 Maddox rod 1034.53 Maddox wing 105


List of Figures xv

4.54 Hess screen 1064.55 Lees screen 1064.56 Arc perimeter 1094.57 Goldmann perimeter 1094.58 Octopus perimeter 1104.59 Six vectors for uniocular rotations 1114.60 Objective assessment of torsion 1124.61 Diplopia chart of IV nerve palsy 1144.62 Diplopia chart of VI nerve palsy 1144.63 Bar reading 1164.64 Stereograms 1175.1 Post-fixational blindness 1346.1 Classification of esotropia 1396.2 Infantile esotropia 1426.3 Intermittent fully accommodative esotropia 1476.4 Intermittent convergence excess esotropia 1496.5 Classification of exotropia 1566.6 Constant exotropia 1576.7 Intermittent distance exotropia 1606.8 Hypertropia 1726.9 Pseudostrabismus 1748.1 Neutral density filter bar 200

11.1 A pattern 23311.2 V pattern 23414.1 Right III nerve palsy 27414.2 Hess chart of right III nerve palsy 27514.3 Hess chart of left inferior rectus palsy 27614.4 Hess chart of right inferior oblique palsy 27714.5 Left IV nerve palsy 28214.6 Hess chart of left IV nerve palsy 28314.7 Field of binocular single vision of left IV nerve palsy 28414.8 Right VI nerve palsy 29014.9 Hess chart of right VI nerve palsy 29014.10 Field of binocular single vision of right VI nerve palsy 29115.1 Duane’s retraction syndrome 31415.2 Hess chart of Duane’s retraction syndrome 31515.3 Field of binocular single vision of Duane’s retraction

syndrome315

15.4 Right Brown’s syndrome 32115.5 Hess chart of right Brown’s syndrome 32215.6 Field of binocular single vision of right Brown’s syndrome 32315.7 Thyroid eye disease 32915.8 Hess chart of thyroid eye disease 33015.9 Hess chart of unilateral thyroid eye disease 331


xvi List of Figures

15.10 Field of binocular single vision of thyroid eye disease 33115.11 Left orbital floor fracture 33515.12 Hess chart of left orbital floor fracture 33615.13 Hess chart of right medial wall fracture 33715.14 Field of binocular single vision of left orbital floor fracture 33718.1 Nystagmus; early onset 36918.2 Nystagmus; late onset 37118.3 Nystagmus velocity 37419.1 Hess chart of right internuclear ophthalmoplegia 38819.2 Field of binocular single vision of right internuclear

ophthalmoplegia389

19.3 Internuclear ophthalmoplegia and one and a halfsyndrome – site of lesions

390

Chart 1 Eso-deviations 415Chart 2 Exo-deviations 416Chart 3 Microtropia 416


List of Tables

1.1 Primary, secondary and tertiary muscle actions 104.1 Age-related visual acuity norms 50

10.1 Differences between congenital and acquired defects 22510.2 Differences between neurogenic and mechanical defects 22510.3 Torticollis differential diagnosis 22914.1 Differences of superior oblique and superior rectus palsy 28514.2 Differences of unilateral and bilateral superior oblique palsy 285


xviii

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SECTION I

1


2


1 Extraocular Muscle Anatomyand Innervation

This chapter outlines the anatomy of the extraocular muscles and their innervationand associated cranial nerves (II, V, VII and VIII).

There are four rectus and two oblique muscles attached to each eye. The rectusmuscles originate from the Annulus of Zinn, which encircles the optic foramen andmedial portion of the superior orbital fissure (Fig. 1.1). These muscles pass forwardin the orbit and gradually diverge to form the orbital muscle cone. By means of atendon, the muscles insert into the sclera anterior to the rotation centre of the globe(Fig. 1.2).

The extraocular muscles are striated muscles. They contain slow fibres, whichproduce a graded contracture on the exterior surface, and fast fibres, which producerapid movements on the interior surface adjacent to the globe. The slow fibres con-tain a high content of mitochondria and oxidative enzymes. The fast fibres containhigh amounts of glycogen and glycolytic enzymes and less oxidative enzymes thanthe slow fibres. The global layer of the extraocular muscles contains palisade end-ings in the myotendonous junctions, which are believed to act as sensory receptors.Signals from the palisade endings passing to the central nervous system may serveto maintain muscle tension (Ruskell 1999, Donaldson 2000).

Muscle pulleys

There is stereotypic occurrence of connective tissue septa within the orbit andstereotypic organisation of connective tissue around the extraocular muscles(Koornneef 1977, 1979). There is also stability of rectus extraocular muscle bellypaths throughout the range of eye movement, and there is evidence for extraocularmuscle path constraint by pulley attachment within the orbit (Miller 1989, Milleret al. 1993, Clark et al. 1999). High-resolution MRI has confirmed the presence ofthese attachments via connections that constrain the muscle paths during rotationsof the globe (Demer 1995, Clark et al. 1997). CT and MRI scans have shownthat the paths of the rectus muscles remain fixed relative to the orbital wall duringexcursions of the globe and even after large surgical transpositions (Demer et al.

Clinical Orthoptics, Third Edition. Fiona J. Rowe.C© 2012 John Wiley & Sons, Ltd. Published 2012 by Blackwell Publishing Ltd.


4 Clinical Orthoptics

Figure 1.1 Orbital apex.

1996, Clark et al. 1999). It is only the anterior aspect of the muscle that moveswith the globe relative to the orbit.

Histological studies have demonstrated that each rectus pulley consists of anencircling ring of collagen located near the globe equator in Tenon fascia attached tothe orbital wall, adjacent extraocular muscles and equatorial Tenon fascia by sling-like bands, which consist of densely woven collagen, elastin and smooth muscle(Demer et al. 1995, Porter et al. 1996). The global layer of each rectus extraocularmuscle, containing about half of all extraocular muscle fibres, passes through thepulley and becomes continuous with the tendon to insert on the globe. The orbitallayer containing the remaining half of the extraocular muscle fibres inserts on thepulley and not on the globe (Demer et al. 2000, Oh et al. 2001, Hwan et al. 2007).

Figure 1.2 Extraocular muscles.


Extraocular Muscle Anatomy and Innervation 5

The orbital layer translates pulleys while the global layer rotates the globe throughits insertion on the sclera. The inferior oblique muscle also has a pulley that ismechanically attached to the inferior rectus pulley (Demer et al. 1999).

The general arrangement of orbital connective tissues is uniform throughoutthe range of human age from foetal life to the tenth decade. Such uniformitysupports the concept that pulleys and orbital connective tissues are important for themechanical generation and maintenance of ocular movements (Kono et al. 2002).

Ocular muscles

Medial rectus muscle

This muscle originates at the orbital apex from the medial portion of the Annulusof Zinn in close contact with the optic nerve. It courses forward for approximately40 mm along the medial aspect of the globe and penetrates Tenon’s capsule roughly12 mm from the insertion. The last 5 mm of the muscle are in contact with theeye and the insertion is at 5.5 mm from the limbus with a width of 10.5 mm. Themuscle is innervated by the inferior division of the III nerve, which enters the muscleon its bulbar side. Its function is adduction of the eye (Fig. 1.3).

Lateral rectus muscle

This muscle arises by two heads from the upper and lower portions of the An-nulus of Zinn where it bridges the superior orbital fissure. It courses forward forapproximately 40 mm along the lateral aspect of the globe and crosses the inferioroblique insertion. It penetrates Tenon’s capsule at roughly 15 mm from the inser-tion and the last 7–8 mm of the muscle is in contact with the eye. The insertion is at

Figure 1.3 Medial rectus action.



Figure 1.4 Lateral rectus action.

7 mm from the limbus with a width of 9.5 mm. The muscle is innervated by the VInerve, which enters the muscle on its bulbar side. Its function is abduction of theeye (Fig. 1.4).

Superior rectus muscle

This muscle arises from the superior portion of the Annulus of Zinn and coursesforward for approximately 42 mm along the dorsal aspect of the globe form-ing an angle of 23◦ with the sagittal axis of the globe. Superiorly, it is in closecontact with the levator muscle. It penetrates Tenon’s capsule at roughly 15 mmfrom the insertion and the last few mms of the muscle are in contact with theeye. The insertion is at 7.7 mm from the limbus with a width of 11 mm. Themuscle is innervated by the superior division of the III nerve, which enters the mus-cle on its bulbar side. Its functions are elevation, intorsion and adduction of theeye (Fig. 1.5).

Inferior rectus muscle

This muscle arises from the inferior portion of the Annulus of Zinn and coursesforward for approximately 42 mm along the ventral aspect of the globe formingan angle of 23◦ with the sagittal axis. It penetrates Tenon’s capsule roughly 15 mmfrom the insertion and the last few millimetres of the muscle are in contact with theeye as it arcs to insert at 6.5 mm from the limbus. The width of insertion is 10 mm.The muscle is innervated by the inferior division of the III nerve, which enters themuscle on its bulbar side. Its functions are depression, extorsion and adduction ofthe eye (Fig. 1.6).


Extraocular Muscle Anatomy and Innervation 7

Figure 1.5 Superior rectus action. The course of the superior rectus is at an angle of 23◦ tothe medial wall of the orbit. Actions in adduction are principally intorsion and adduction; in theprimary position, actions are elevation, intorsion and adduction; action in abduction isprincipally elevation.

Superior oblique muscle

This muscle originates from the orbital apex from the periosteum of the bodyof the sphenoid bone, medial and superior to the optic foramen. It courses for-ward for approximately 40 mm along the medial wall of the orbit to the trochlea

Figure 1.6 Inferior rectus action. The course of the inferior rectus is at an angle of 23◦ to themedial wall of the orbit. In adduction, the actions are principally extorsion and adduction; inthe primary position, actions are depression, extorsion and adduction; action in abduction isprincipally depression.



Figure 1.7 Superior oblique action. The course of the superior oblique tendon is at an angleof 51◦ to the medial wall of the orbit. Action in adduction is depression; in the primaryposition, actions are depression, intorsion and abduction; in abduction, action is intorsion.

(a V-shaped fibrocartilage that is attached to the frontal bone). The trochlear regionis described by Helveston et al. (1982).

The muscle becomes tendonous roughly 10 mm posterior to the trochlea and isencased in a synovial sheath through the trochlea. From the trochlea, it coursesposteriorly, laterally and downwards forming an angle of 51◦ with the visual axisof the eye in the primary position. It passes beneath the superior rectus and insertson the upper temporal quadrant of the globe ventral to the superior rectus. Itsinsertion is fanned out in a curved line 10–12 mm in length. The muscle is inner-vated by the IV nerve that enters the muscle on its upper surface roughly 12 mmfrom its origin. Its functions are intorsion, depression and abduction of the eye(Fig. 1.7).

Inferior oblique muscle

This muscle arises from the floor of the orbit from the periosteum covering theanteromedial portion of the maxilla bone. It courses laterally and posteriorly forapproximately 37 mm, forming an angle of 51◦ with the visual axis. It penetratesTenon’s capsule near the posterior ventral surface of the inferior rectus, crossesthe inferior rectus and curves upwards around the globe to insert under the lateralrectus just anterior to the macular area. The muscle is innervated by the inferiordivision of the III nerve that enters the muscle on its bulbar surface. Its functionsare extorsion, elevation and abduction of the eye (Fig. 1.8).

Figure 1.9 illustrates the muscle insertions in relation to the anterior segmentof the eye. Figure 1.10 illustrates the positions of main action of each extraocularmuscle and Table 1.1 illustrates all primary, secondary and tertiary muscle actions.


Figure 1.8 Inferior oblique action. The course of the inferior oblique is at an angle of 51◦ tothe medial wall of the orbit. Action in adduction is elevation; actions in the primary positionare elevation, extorsion and abduction; in abduction, action is extorsion.

Figure 1.9 Extraocular muscle insertions. SR, superior rectus; MR, medial rectus;LR, lateral rectus; IR, inferior rectus.

SRIOIOSR

LR RIGHT LRLEFTMRMR

IRSOSOIR

Lateral rectus LR Inferior rectus IR Superior rectus SR

Superior oblique SO Inferior oblique IO Medial rectusMR

Figure 1.10 Cardinal positions of gaze – position of main action of extraocular muscles.

9



Table 1.1 Primary, secondary and tertiary extraocular muscle actions.

Muscle Primary action Secondary action Tertiary action

Medial rectus Adduction – –

Lateral rectus Abduction – –

Superior rectus Elevation, maximumin abduction

Intorsion, maximum inadduction

Adduction, maximumin adduction

Inferior rectus Depression, maximumin abduction

Extorsion, maximumin adduction

Adduction, maximumin adduction

Superior oblique Intorsion, maximum inadduction

Depression,maximum inabduction

Abduction, maximumin abduction

Inferior oblique Extorsion, maximumin abduction

Elevation, maximumin adduction

Abduction, maximumin abduction

Levator palpebral superioris

This muscle originates from the under surface of the lesser wing of sphenoid boneabove and in front of the optic foramen by a short tendon that blends with theorigin of the superior rectus. It runs forward and changes directly from horizontalto vertical at the level of the equator of the globe. At approximately 10 mm abovethe superior margin of the tarsus, it divides into anterior and posterior lamellae. Theanterior lamellae form the levator aponeurosis that is inserted into the lower thirdof the entire length of the anterior surface of the tarsus. Its fibres extend to the pre-tarsal portion of the orbit and skin. The posterior lamellae form Muller’s musclethat is attached inferiorly to the superior margin of the tarsus.

Innervation

The extraocular muscles are innervated by the III, IV and VI nerves.

III nerve

The III nerve (third/oculomotor) supplies the superior rectus, inferior rectus, medialrectus, inferior oblique and levator muscles. Its visceral fibres innervate the ciliarymuscle and sphincter pupillary muscle that synapse in the ciliary ganglion.

The nuclei are in the mesencephalon at the level of the superior colliculus. Thereis an elongated mass of cells that form the nuclei. Peripheral motor neurones in-nervate multiply innervated extraocular muscle fibres and central motor neuronesinnervate single innervated muscle fibres. Dorsal nucleus fibres pass to the ipsi-lateral inferior rectus, intermediate nucleus fibres pass to the ipsilateral inferioroblique, ventral nucleus fibres pass to the ipsilateral medial rectus, paramediannucleus fibres pass to the contralateral superior rectus, central caudal nucleus fibrespass to both levator muscles, and the anterior median/Edinger-Westphal nucleus

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