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Anatomy & physiology of eom
This document discusses the anatomy and physiology of the extra-ocular muscles. It begins by describing the intrinsic and extrinsic muscles, their embryology, and structures like the muscle cone and fascia bulbi. It then provides details on each of the six extrinsic eye muscles - superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, and inferior oblique - including their origin, insertion, nerve supply, and actions. The document emphasizes the extrinsic muscles' roles in moving the eye and maintaining clear vision.
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Anatomy & physiology of eom
- 1. Anatomy Physiology Extra-Ocular Muscles Moderator:Dr. Arvind Tenagi Presenter: Dr. Arushi Prakash of 23rd July '15 1 & Dept. of Ophthalmology, JNMC, Belagavi
- 2. Contents • Orbital Muscles- Intrinsic Extrinsic •Embyrology • Muscle Cone • Fascia bulbi • Muscle Pulley • Annulus of Zinn • Spiral of Tillaux • Origin & Insertions • Blood Supply • Nerve Supply • Centre of Rotation • Ocular Movements • Laws of Ocular Motility • Supranuclear Control of Eye Movements • 3rd, 4th, 6th Cranial Nerve Palsies 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 23rd July '15 2
- 3. ORBITAL MUSCLES Extrinsic musclesof eyeball. • Involved in movement of eyeball. Intrinsic muscles • Controls shape of lens and size of pupil. Dept. of Ophthalmology, JNMC, Belagavi 3 23rd July '15
- 4. Intrinsic Muscles • irissphincter, • radial pupilodilator muscles • ciliary muscle • Controlled by autonomic nervous system, work in response to amount of light, closeness of an object (for focusing), etc • serve to focus the eye and control the amount of light entering it Dept. of Ophthalmology, JNMC, Belagavi 4 23rd July '15
- 5. Extrinsic Muscles Involuntary Muscles SuperiorTarsal Muscle Inferior Tarsal Muscle Orbitalis Voluntary Muscles Levator Palpebrae Superioris Superior Rectus Inferior Rectus Medial Rectus Lateral Rectus Superior Oblique Inferior Rectus Dept. of Ophthalmology, JNMC, Belagavi 5 23rd July '15
- 6. Embryology • mesodermal origin, •Perimuscular Connective tissues from neural crest • development beginning at 3– weeks of gestation. • muscles originate from three separate foci of primordial cells- one for the muscles innervated by the oculomotor nerve, one for the superior oblique muscle, one for the lateral rectus muscle. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 6
- 7. Embryology • All EOMdevelop in situ; • receive input from their respective cranial nerves as early as 1 month of gestation. • All of the extraocular muscle and their surrounding tissues are present and in their final anatomical positions by 6 months of gestation, merely enlarging throughout the remainder of gestation 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 7
- 8. Dept. of Ophthalmology,JNMC, Belagavi 11 Muscle cone The rectus muscle forms the muscle cone within the orbit with apex at their origin and base at their penetration of tenon’s capsule. Each muscle is surrounded by fibrous capsule which are attached by thin continuous membrane called intermuscular septum Intermuscular septum divides orbital fat pad into extraconal fat and intraconal fat which help to maintain cushioning effects. Intermuscular septum fuses with tenon 3mm from the limbus Fibrous capsule Intermuscular septum Intraconal fat Extraconal fat Muscle cone
- 9. Dept. of Ophthalmology,JNMC, Belagavi 12 The Fascia Bulbi The tenon capsule/fascia bulbi is an envelope of elastic fibrous connective tissue Form protective covering at site of attachment of EOM Tenon capsule fuses with optic nerve sheath posteriorly and anteriorly with intermascular septum, 3 mm posterior to the limbus. EOM penetrates the tenon capsule 10 mm posterior to their insertion Tenons are divided into anterior and posterior parts Tenon capsule 10mm
- 10. Dept. of Ophthalmology,JNMC, Belagavi 13 Muscle pulley As the EOM penetrates the tenon capsule the connective tissue forms the sleeves around the muscles creating muscle pulleys. Discrete rings of dense collagen tissue encircling EOM & are about 2mm length Pulley redirects the muscle and acts as functional origin it also prevents displacement of muscle during movement Because of pulley mechanism muscle are inflect at the insertion forming angle with the orbital axis. muscle pulley Pulley Angle
- 11. Dept. of Ophthalmology,JNMC, Belagavi Extra ocular Muscles:Origin Superior ObliqueLevator palpebrae superioris Medial Rectus Lateral Rectus Superior Rectus Inferior Rectus Inferior Oblique 14
- 12. Dept. of Ophthalmology,JNMC, Belagavi Oval, fibrous ring at the orbital apex. Structures passing through the annulus: 1. Occulomotor nerve (superior and inferior divisions) 2. Abducens Nerve 3. Optic Nerve 4. Nasociliary Nerve 5. Ophthalmic Artery Annulus of Zinn 15
- 13. 23rd July '15 16 23rdJuly '15 Clinical Significance Retrobulbar neuritis ○ Origin of SUPERIOR AND MEDIAL RECTUS are closely attached to the dural sheath of the optic nerve, which leads to pain during upward & inward movements of the globe. Thyroid orbitopathy ○ Medial & Inf.rectus thicken. especially near the orbital apex - compression of the optic nerve as it enters the optic canal adjacent to the body of the sphenoid bone. Ophthalmoplegia ○ Proptosis occur due to muscle laxity.Dept. of Ophthalmology, JNMC, Belagavi
- 14. SPIRAL OF TILLAUX 5.5mm 6.5 mm 6.9 mm 7.7 mm Dept. of Ophthalmology, JNMC, Belagavi 17 23rdJuly '15
- 15. 23rd July '15 18 23rdJuly'15 Dept. of Ophthalmology, JNMC, Belagavi Medial rectus inserts closest to the limbus and is therefore susceptible to injury during ant. segment surgery. Inadvertent removal of the MR is a well known complication of Pterygium removal The Scleral thickness behind the rectus insertion is the thinnest, being only 0.3 mm thick -> chances of scleral perforation while suturing Clinical Significance
- 16. 23rd July '15 1 Dept.of Ophthalmology, JNMC, Belagavi
- 17. 23rd July '15 2 LEVATORPALPEBRAE SUPERIORIS Origin: Orbital surface of lesser wing of sphenoid bone, anterosuperior to optic canal. Insertion: Splits in two lamina Superior lamina (voluntary) to Skin of upper eyelid & anterior surface of superior tarsal plate Inferior lamina (Muller’s muscle)(involuntary) to upper margin of superior tarsus (superior tarsal or muller’s muscle) & superior conjunctival fornix Dept. of Ophthalmology, JNMC, Belagavi
- 18. 23rd July '15 2 •NERVE SUPPLY- Upper division of occulomotor nerve. • ACTION- Elevation of upper eyelid. • Ptosis Drooping of upper eyelid. • Complete ptosis-injury to occulomotor nerve. • Partial ptosis-disruption of postganglionic sympathetic fibres from superior cervical sympathetic ganglion. Dept. of Ophthalmology, JNMC, Belagavi
- 19. 23rd July '15 22Dept.of Ophthalmology, JNMC, Belagavi
- 20. SUPERIOR RECTUS MUSCLE •Origin-Superior part of common tendon of zinn. • Insertion-inserted into sclera by flat tendinous insertion(10mm broad)about 7.7 mm behind sclero-corneal junction. • Nerve supply-superior division of occulomotor nerve. Dept. of Ophthalmology, JNMC, Belagavi23rd July '15 23
- 21. Action of SuperiorRectus • Primary action is elevation . . But since the insertion on the globe is lateral as well as superior, contraction will produce rotation about the vertical axis toward midline • Thus secondary action is adduction • Finally, because the insertion is oblique, contraction produces torsion nasally Intorsion. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 24
- 22. INFERIOR RECTUS • Origin-inferiorpart of common tendon of zinn • Insertion-in the sclera 6.5 mm behind sclero corneal junction. • Nerve supply-inferior division occulomotor nerve. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 25
- 23. • Fascial attachmentsbelow attached to inferior lid coordinate depression and lid opening. • Fascia below Inf. Rectus and Inf. Oblique contribute to the suspensory ligament of lockwood. • ACTIONS- Primary depressor. Subsidiary actions are adduction and extorsion. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 26
- 24. MEDIAL RECTUS • Origin-annulusof zinn and from optic nerve sheath. • Insertion-in sclera 5.5mm behind sclero-corneal junction. • Nerve supply-lower division of occulomotor nerve. • Fascial expansion from muscle sheath forms the medial check ligament and attach to medial wall of orbit. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 27
- 25. • Innervation isvia cranial nerve III, the oculomotor nerve, and the specific branch runs along the inside of the muscle cone, on the lateral surface. • The superior oblique, ophthalmic artery and nasociliary nerve all lie above the medial rectus. • ACTION- Primary adductor of the eye. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 28
- 26. LATERAL RECTUS • Origin-annulusof zinn. • Insertion-in the sclera 6.9mm behind sclerocorneal junction. • Nerve supply-abducens nerve which enters the muscle on the medial surface. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 29
- 27. • The lacrimalartery and nerve run along the superior border. • The abducens nerve, ophthalmic artery and ciliary ganglion lie medial to the lateral rectus and between it and the optic nerve. • ACTION- Primary abductor of eye. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 30
- 28. SUPERIOR OBLIQUE • Longestand thinnest intraorbital muscle, the muscle ends before t he trochlea, tendon is 2.5 cm, smooth movement through trochlea. • Origin-body of sphenoid above and medial to optic canal.Passes along superomedial part of orbit and ends in a tendon. • Insertion-Posterosuperior quadrant of sclera behind equator of eyeball. • Nerve supply-trochlear nerve entering it approximately one third of the distance from the origin to the trochlea. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 31
- 29. ACTIONS Primary action-intorsion. Subsidiary actions-abduction and depression. Adducted position-depression. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 32
- 30. INFERIOR OBLIQUE • Origin-Anteromedialpart of orbital floor lateral to nasolacrimal groove. • Insertion-posteroinferior surface of globe near the macula. • Nerve supply-inferior division of occulomotor nerve enters the muscle laterally at the junction of the inferior oblique and inferior rectus muscles. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 33
- 31. ACTIONS • Primary action-extorsion. •Subsidiary actions-elevations and abduction. • Causes elevation only in adducted position of eyeball. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 34
- 32. Origins/Insertions of Oblique muscles 23rdJuly '15 Dept. of Ophthalmology, JNMC, Belagavi 35
- 33. Dept. of Ophthalmology,JNMC, Belagavi 36 23rdJuly '15 Blood supply EOM are supplied by the branches of ophthalmic artery. 1. Muscular branches 2. Lacrimal braches As the ophthalmic artery enter the muscle cone through the optic canal it braches to Lateral and Medial muscular branches Medial muscular branch Lateral muscular branch
- 34. Dept. of Ophthalmology,JNMC, Belagavi 37 23rdJuly '15 • Muscular artery course along with CN 3 to enter rectus muscle at the junction of posterior and middle one third. • Lateral muscular branches- a. lateral rectus b. sup rectus c. LPS d. SO • Medial muscular branches- a. medial rectus b. inferior rectus c. IO • Lacrimal branch-LR and SR
- 35. Dept. of Ophthalmology,JNMC, Belagavi 38 23rdJuly '15 Anterior ciliary artery (ACA) • 7 in no. • Branches of muscular arteries • Along tendons of muscles and pierce sclera 4 mm from the limbus and enter eyeball • Join the LPCA to form the major arterial circle of iris. • Supplies -- Cilliary body and iris. • ACA runs in pair in each rectus muscle except LR which has only one ACA Muscular branch LR with single ACA Clinical correlates: interruption of ACA during surgery involving more than two rectus muscle can result in anterior segment ischemia!
- 36. Dept. of Ophthalmology,JNMC, Belagavi 39 23rdJuly '15 Venous drainage of EOM • The venous drainage of the extraocular muscles is via the superior and inferior orbital veins to ophthalmic veins Anterior ciliary vein Cavernous sinus Inferior ophthalmic vein Superior ophthalmic vein Superior orbital vein inferior orbital vein Clinical correlates: Secondary Perimuscular infection following EOM trauma can spread infection to cavernous sinus . Cavernous vascular disease can present as opthalmoplegia and proptosis
- 37. 23rdJuly '15 Dept. ofOphthalmology, JNMC, Belagavi Nerve Supply of Extraocular Muscles Superior division of oculomotor:- levator palpebrae superioris, superior rectus Inferior division of oculomotor:- medial rectus, inferior oblique, inferior rectu Trochlear nerve - superior oblique Abducent nerve - lateral rectus 23rd July '15 41 AL3SO4LR
- 38. 23rd July '15 42 23rdJuly'15 Dept. of Ophthalmology, JNMC, Belagavi Structure of EOM Each EOM consist of 2 layers – 1. Orbital layer which located superficially near the orbital wall 2. Globar layer which is located more deeper • Fibers of Global layer become contiguous with tendon to insert on the globe ; orbital layer is inserted on muscle pulley
- 39. 23rd July '15 43 23rdJuly'15 Dept. of Ophthalmology, JNMC, Belagavi Microanatomy of EOM • EOM are striated muscles with bundles of muscle fibers(functional units) which is made up of actin and myocin filaments • Compared to skeletal muscle(SM)EOM fibers are small and numerous with abundant nucleus which are highly innervated- ratio of nerve to muscle fiber of 1:3-1:5 compared 1: 50-1:125 of SM • EOM has more contractile units • This accounts for very precise and rapid movement of eye by EOM
- 40. 23rd July '15 44 23rdJuly'15 Dept. of Ophthalmology, JNMC, Belagavi EOM Fibers Two type 2.Multiply innervated fibers (MIFs)1.Singly innervated fibers(SIFs) • Large diameter • Arranged irregularly • Abundant mitochondria Multiply innervated Many branches 1 nerve as en grappe Mostly found in orbital layer of EOM Allows fatigue resistant smooth ocular movement • Small diameter • Regularly arranged • Fewer mitochondria Singly innervated 1 nerve, 1 branch as en plaque Mostly found in globular layer of EOM Allows rapid, saccadic and precise movements
- 41. Disorders of eyeMovements • Strabismus- misalignment of the eyes such that disparate images reach corresponding parts of each retina, disruption binocuular vision • Nystagmus- bilateral, involuntary, and conjugate oscillation of the eyes • Congenital Cranial Dysinnnervation Disorders (CCDD)- rare, non- progressive inherited strabismic disorders characterized by congenital fibrosis of one or more of the EOM resulting in a static eye position or directional impairment. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 45
- 42. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 46
- 43. Dept. of Ophthalmology,JNMC, Belagavi 47 Diseases where EOM are Spared Etiology Limb Muscle Pathology Duchenne muscular dystrophy X- linked genetic mutation of dystrophin gene Progressive, Muscle wasting and weakness Becker Muscular Dystrophy X-linked genetic mutation of dystrophin gene, less severe phenotype than Duchenne Progressive, Muscle wasting and weakness α, γ, and δ- sarcoglycan deficiency (limb girdle muscular dystrophy) Mutation of sarcoglycan gene Progressive, Muscle wasting and weakness Laminin α2- congenital muscular dystrophy Mutation of laminin α2 gene Progressive, Muscle wasting and weakness Amyotropic lateral sclerosis Mutations of superoxide dismutase gene; mitochondriopathy Progressive, Muscle wasting and paralysis
- 44. Dept. of Ophthalmology,JNMC, Belagavi 48 Diseases where EOM are primarily or preferentially involved Etiology EOM pathology amd /or symptoms Graves’s Opthalmopathy Autoimmune disease of the EOM, resulting in enlargement; presumably due to one or more shared antigens with the thyroid gland Inflammatory orbitopathy, myopathy CPEO (Chronic Progressive External Ophthalmoplegia) Mitochondrial DNA deletion, mutation of DNA polymerase- gamma gene Accumulation of mutant mitochondria leads to muscle paralysis Kearns- Sayre Syndrome Longer mitochondrial DNA deletions than CPEO Accumulation of mutant mitochondria leads to muscle paralysis
- 45. Dept. of Ophthalmology,JNMC, Belagavi 49 Diseases where EOM are primarily or preferentially involved Etiology EOM pathology amd /or symptoms Ocular Myasthenia Gravis Autoimmune disease to either the acetylcholine receptor or MuSK EOM and levator palpebrae superioris muscle weakness Myotonic Dystrophy type 1 Expansion of CTG repeat within the DMPK gene Saccadic slowing, optokinetic nystagmus Myotonic dystrophy type 2 Expansion of a CCTG repeat expansion of the CNBP gene Rebound Nystagmus Childhood strabismus Unknown. Complex Genetic cause ? Under- or overactive EOM with loss of binocularity and eye alignment in primary gaze
- 46. Dept. of Ophthalmology,JNMC, Belagavi 50 Diseases where EOM are primarily or preferentially involved Etiology EOM pathology amd /or symptoms Congenital Nystagmus Missense mutation in FRMD7 gene; function unknown. Clinically heterogenous; multiple genes involved Conjugate, horizontal eye oscillations, in primary or eccentric gaze Miller-Fisher Syndrome Autoimmmune disease against ganglioside GQ1b/GT1a EOM paralysis Congenital cranial dysinnervation disorders Specific gene mutation for each type EOM weaknness or absence
- 47. 23rd July '15 51 23rdJuly'15 • The primary position of the eye is that position from which all other ocular movements are initiated • A total of nine positions of gaze have been described. One primary 4 secondary 4 tertiary positions BASIC KINEMATICS Dept. of Ophthalmology, JNMC, Belagavi
- 48. 23rd July '15 52 23rdJuly'15 Primary position of gaze • Defined by Scobee Position of the eyes in binocular vision when, with the head erect, the object of regard is at infinity and lies at the intersection of the sagittal plane of the head and a horizontal plane passing through the centres of rotation of the two eyeballs Dept. of Ophthalmology, JNMC, Belagavi
- 49. 23rd July '15 53 23rdJuly'15 Secondary position of gaze • Positions assumed by the eyes while looking • straight up, (supraversion) • straight down, (infraversion) • to the right, (dextroversion) • and to the left (levoversion) Dept. of Ophthalmology, JNMC, Belagavi
- 50. 23rd July '15 54 23rdJuly'15 Tertiary position of gaze • Positions assumed by the eyes when combination of vertical and horizontal movements occur. • Dextroelevation • Dextrodepression • Levoelevation • levodepression Dept. of Ophthalmology, JNMC, Belagavi
- 51. 23rd July '15 55 Motionof an Eye • To describe eye motions we need a set of defined axes (Fick’s Axes -) • X axis : nasal -> temporal • Y axis: anterior -> posterior • Z axis: superior -> inferior • These axes intersect at the center of rotation - a fixed point, defined as 13.5 mm behind cornea. Dept. of Ophthalmology, JNMC, Belagavi
- 52. 23rd July '15 56 Centreof Rotation In primary position - lies 13.5 mm behind the apex of cornea. In big myopic eyes, the centre of rotation is a bit farther posterior and in small hyperopic eyes it is a bit anterior to this ideal position The X and Z axis lie in the same plane. This plane passing through the centre of rotation of the eye and containing the X and Z axes is called Listing’s plane Dept. of Ophthalmology, JNMC, Belagavi
- 53. 23rd July '15 57Dept.of Ophthalmology, JNMC, Belagavi Ocular movements Ocular movement occurs around the axis of Fick 3 basic ocular movements 1.Ductions – 2.Version- monocular movement around the axis of Fick Binocular, simultaneous, conjugate movements- (in same direction) Binocular, simultaneous, disjugate /disjunctive movement-in opposite direction 3.Vergences- 1.Convergence 2.divergence
- 54. Dept. of Ophthalmology,JNMC, Belagavi 58 23rdJuly '15 Ductions Are tested by occluding one eye and asking the patient to follow target in each direction of gaze Ductions consist of following- 1.adduction-MR 4.depression- 2.abduction-LR 6.Extorsion (IO) 3.Elevation (SR) 5.Intorsion (SO) OD
- 55. Dept. of Ophthalmology,JNMC, Belagavi 59 23rdJuly '15 Version Tested with both eye open and asking patient to follow a target in each direction of gaze. Following are the various gaze of versions-9 cardinal gaze 3.Dextroelevation (ODSR+OSIO) 2.Destroversion ODLR+OSMR) 5.Laevoversion (OSLR+ODMR) 6.Laevoelevation (OSSR+ODIO) 7.Laevodrepression (OSIR+ODSO)9.drepression 8.elevation 1.Primary position 4.Dextrodrepression (ODIR+OSSO)
- 56. 23rd July '15 60Dept.of Ophthalmology, JNMC, Belagavi MUSCLES CAUSING MONOCULAR MOVEMETS • Primary muscle action is the main and most powerful direction in which the eye moves when the muscle is contracted • Secondary muscle action is the second direction in which the eye moves when that muscle is contracted, but is not the main or most important action • Tertiary muscle action is the least powerful direction in which the eye moves as a result of contraction of the muscle
- 57. 23rd July '15 61Dept.of Ophthalmology, JNMC, Belagavi • When the globe is abducted to 23°, the visual and orbital axis coincide. In this position superior rectus acts as a pure elevator. • If the globe were adducted to 67° the angle between the visual and orbital axis would be 90° In this position SR would act as a pure intorter.
- 58. 23rd July '15 62Dept.of Ophthalmology, JNMC, Belagavi • When the globe is adducted to 51 ͦ, the visual axis coincides with the line of pull of the muscle, the SO acts as a depressor • When the globe is abducted to 39 ͦ, the visual axis and the SO make an angle of 90 ͦ, the SO causes only intorsion
- 59. 63 23rd July '15 63 MUSCLEPRIMARY ACTION SECONDARY ACTION TERTIARY ACTION MR ADDUCTION __________ ____________ LR ABDUCTION __________ ____________ SR ELEVATION INTORSION ADDUCTION IR DEPRESSION EXTORSION ADDUCTION SO INTORSION DEPRESSION ABDUCTION IO EXTORSION ELEVATION ABDUCTION
- 60. 23rd July '15 64Dept.of Ophthalmology, JNMC, Belagavi Superior Oblique Inferior Oblique Superior rectus Inferior rectus Medial rectus Lateral rectus
- 61. 23rd July '15 65Dept.of Ophthalmology, JNMC, Belagavi Laws of ocular motility • Agonist – Any particular EOM producing specific ocular movement • Synergists – Muscles of the same eye that move the eye in the same direction
- 62. 23rd July '15 66Dept.of Ophthalmology, JNMC, Belagavi • Antagonists – A pair of muscles in the same eye that move the eye in opposite directions • Yoke muscles ( contralateral synergists) – Pair of muscles, one in each eye , that produce conjugate ocular movements
- 63. 23rd July '15 67Dept.of Ophthalmology, JNMC, Belagavi • Agonist-Antagonist Pairs (in the Same Eye) • Medial rectus–lateral rectus • Superior rectus–inferior rectus • Superior oblique–inferior oblique • Paired Agonists (in Separate Eyes) • Left medial rectus–right lateral rectus • Left lateral rectus–right medial rectus • Left superior rectus–right inferior oblique • Left inferior rectus–right superior oblique • Left superior oblique–right inferior rectus • Left inferior oblique–right superior rectus
- 64. 23rd July '15 68Dept.of Ophthalmology, JNMC, Belagavi Listing’s Law • All achieved eye orientations can be reached by starting from one specific "primary" reference orientation and then rotating about an axis that lies within the plane orthogonal to the primary orientation's gaze direction (line of sight / visual axis). • This plane is called Listing's plane. • According to Listing cycloversion is 0°
- 65. 23rd July '15 Dept.of Ophthalmology, JNMC, Belagavi 69 • An equal and simultaneous innervation flows from the brain to a pair of yoke muscles which contracts simultaneously in different binocular movements • Ex. Right LR and Left MR during dextroversion • Applies to all normal eye movements HERING’S LAW OF EQUAL INNERVATION
- 66. 23rd July '15 Dept.of Ophthalmology, JNMC, Belagavi 70 • States that increased innervation to a contracting agonist muscle is accompanied by reciprocal inhibition of its antagonist • Ex. During detroversion there is increased innervation to right LR and left MR accompanied by decreased flow to right MR and left LR SHERRINGTON’S LAW OF RECIPROCAL INNERVATION
- 67. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 71 Applied Anatomy • Abnormal deviation of eyeball is known as Squint (Strabismus). • Paralysis of Lateral rectus due to damage to Abducent nerve leads to Medial Squint. • Damage to Occulomotor nerve leads to paralysis of all muscles of eye except Superior oblique and lateral rectus leading to Lateral Squint and Ptosis-Dropping of Eyelid. • Damage to Trochlear nerve cause paralysis of superior oblique muscle causing diplopia while looking downwards. Medial Squint Lateral Squint and Ptosis -Dropping of Eyelid. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 71
- 68. 23rd July '15 Dept.of Ophthalmology, JNMC, Belagavi 72 Supranuclear Control of Eye Movements
- 69. 23rd July '15 73Dept.of Ophthalmology, JNMC, Belagavi Functional Classification of Eye Movement Systems Direct the fovea to an object of interest: • Saccades • Smooth pursuit • Vergence Hold images steady on the retina: • Fixation • Vestibulo-ocular reflex (VOR) • Optokinetic nystagmus
- 70. 23rd July '15 74Dept.of Ophthalmology, JNMC, Belagavi Saccades • Rapid eye movements to direct the fovea to a target whose image is falling peripherally on the retina or a voluntary command eye movement. • Velocity: 300 – 700° / sec. • Initiation by: Frontal eye field or pariteal eye field
- 71. Neural Control ofSaccades Gaze Centers cueflash.com/decks/CONTROL_OF_EYE_MOVEMENTS_-_57 • Horizontal - Paramedian pontine reticular formation (PPRF) • Vertical - Rostral interstitial nucleus (rostral iMLF)
- 72. 23rd July '15 76Dept.of Ophthalmology, JNMC, Belagavi Pursuit • Following movements with the purpose of maintaing the image of a slowly moving samll object on the fovea. • Velocity: up to 100° / sec. • Initiation by: Temporo-occipital junctiion
- 73. 23rd July '15 77Dept.of Ophthalmology, JNMC, Belagavi Vergence Eye Movements • Maintain fusion of images when targets move towards or away from the eyes. • Velocity: 20° / sec. • Control center lies in the midbrain
- 74. 23rd July '15 78Dept.of Ophthalmology, JNMC, Belagavi Fixation • Purpose- Maintaing the image of the object of regard on the fovea • Supplementary eye fields maintain fixation with the eyes in specific orbital locations and also inhibits visually evoked saccadic reflexes. • Frontal eye field is involved in changing fixation (disengaging)
- 75. 23rd July '15 79Dept.of Ophthalmology, JNMC, Belagavi Vestibulo Vestibulo-ocular Reflex (VOR) ocular Reflex (VOR) • Maintains fixation during brief head movements. • Input from vestibular nuclei travels through MLF to ocular motor nuclei. • Initiation by: Otolith receptors and semicircular canalas. Second order neuronn are in the vestibular nuclei
- 76. 23rd July '15 80Dept.of Ophthalmology, JNMC, Belagavi Optokinetic Nystagmus (OKN) • Maintains fixation during target movement or sustained head movements. • Fast & slow phases. • Fast phase is controlled by contralateral frontal eye field & slow phase by ipsilateral parieto-occipito-temporal area.
- 77. 3rd Nerve Palsy •Right 3rd Nerve palsy is charactarized by the following • Weakness of the levator causing profound ptosis, due to which there is often no diplopia. • Unopposed action of the lateral rectus causing the eye to be abducted in the primary position. The intact superior oblique muscle causes intorsion of the eye at rest which increases on attempted downgaze. • Normal abduction because the lateral rectus is intact. • Weakness of the medial rectus limiting adduction.23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 81 23rdJuly '15
- 78. • Weakness ofsuperior rectus and inferior oblique, limiting elevation. • Weakness of inferior rectus limiting depression. • Parasympathetic palsy causing a dilated pupil associated with defective accommodation. • Partial involvement will produce milder degrees of ophthalmoplegia 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 82 23rdJuly '15
- 79. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 83
- 80. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 84 23rdJuly '15
- 81. Left 4th nervepalsy 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 85 23rdJuly '15 • Characterized by: • Left hypertropia (‘left-over-right’) in the primary position. • Increase in left hypertropia on right gaze due to left inferior oblique overaction. • Limitation of left depression on adduction. Normal left abduction. Normal left depression. • Normal left elevation
- 82. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 86
- 83. . 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 87 23rdJuly '15 • Abnormal head posture avoids diplopia which is vertical, torsional and worse on looking down. • To intort the eye (alleviate excyclotorsion) there is contralateral head tilt to the right. • To alleviate the inability to depress the eye is adduction, the face is turned to the right and the chin is slightly depressed. • The left eye cannot look down and to the right or intort – the head therefore does this and thus compensates
- 84. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 88
- 85. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 89 23rdJuly '15
- 86. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 90 • Acute left 6th nerve palsy • Left esotropia in the primary position. • Marked limitation of left abduction. Acute 6th nerve palsy 23rdJuly '15 90
- 87. Long-standing left 6thnerve palsy Dept. of Ophthalmology, JNMC, Belagavi • Left esotropia in the primary position due to unopposed action of the left medial rectus. • The deviation is characteristically worse for a distant target and less or absent for near fixation. Marked limitation of left abduction due to weakness of the left lateral rectus. • Normal left adduction. 23rdJuly '15 91
- 88. 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 92 23rdJuly '15
- 89. Differential Diagnosis • Myastheniagravis can mimic virtually any ocular motility defect. Distinguishing features include variability of diplopia and other signs such as lid fatigue and the Cogan twitch sign. • Restrictive thyroid myopathy involving the medial rectus may give rise to limitation of abduction. Associated features include orbital and eyelid signs and a positive forced duction. • Medial orbital wall blowout fracture with entrapment of the medial rectus, giving rise to limitation of abduction. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 93 23rdJuly '15
- 90. Differential Diagnosis • Orbitalmyositis involving the lateral rectus is characterized by weakness of abduction and pain when this is attempted. • Duane syndrome is a congenital condition characterized by defective abduction and narrowing of the palpebral fissure on adduction. • Convergence spasm typically affects young adults and is characterized by convergence with miosis and increased accommodation. • Divergence paralysis is a rare condition which may be difficult to distinguish from unilateral or bilateral 6th nerve palsy. However, unlike 6th nerve palsy the esotropia may remain the same or diminish on lateral gaze. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 94 23rdJuly '15
- 91. 95 • Wolff’s Anatomyof Eye -8th edition • Parson’s Disease of the Eye-21st ed • Adler’s Physiology of the Eye- 11th ed • Jack.J.Kanski Brad Bowling Clinical Ophthalmology -7th ed • Yanoff & Duker Ophthalmology- 3rd ed • http://www.downstate.edu/ophthalmology/p df/Grand-Rounds-Arun-Joseph.pdf • http://rmsolutions.net/rmfiles/Retina2010/0 14002.pdf • http://91.146.107.207/~wwwacnr/wp-
- 92. Thankyou 23rd July '15Dept. of Ophthalmology, JNMC, Belagavi 96
Editor's Notes
- #39 LPCA- long posterior ciliary artery.
- #61 With the eye in primary position, the horizontal rectus muscles are purely horizontal movers around the z-axis (the vertical axis), and they have a primary action only. The vertical rectus muscles have a direction of pull that is mostly vertical as their primary action, but the angle of pull from origin to insertion is inclined 23° to the visual axis, giving rise which is defined as any rotation of the vertical corneal meridians.
- #66 Agonist Any particular EOM producing specific ocular movement Ex. Right LR for right eye abduction Synergists Muscles of the same eye that move the eye in the same direction Ex. Right SR and right IO for right eye elevation
- #67 Antagonists A pair of muscles in the same eye that move the eye in opposite directions Ex. right LR and right MR Yoke muscles ( contralateral synergists) Pair of muscles, one in each eye , that produce conjugate ocular movements Ex. right LR and left MR in dextroversion
- #76 PPRF and MLF combined lesions on the same side give rise to the ‘one-and-a-half syndrome’ which is characterized by a combination of ipsilateral gaze palsy and INO so that the only residual movement is abduction of the contralateral eye which also exhibits ataxic nystagmus