EXTRA OCULAR MUSCLES

Extra-Ocular MusclesBy/Mohamed Ahmed El –Shafie

Assistant Lecturer in ophthalmology department KafrELShiekh University

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ORBITAL MUSCLES

Extrinsic muscles of eyeball.• Involved in movement of eyeball.

Intrinsic muscles• Controls shape of lens and size of pupil.

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Intrinsic Muscles• iris sphincter, • 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

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vedio

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Extrinsic Muscles

Involuntary Muscles

Superior Tarsal Muscle

Inferior Tarsal Muscle

Orbitalis

Voluntary MusclesLevator Palpebrae Superioris

Superior Rectus

Inferior Rectus

Medial Rectus

Lateral Rectus

Superior Oblique

Inferior Rectus 5

Embryology

• mesodermal origin, • Perimuscular Connective tissues from neural crest • development beginning at 3– weeks of gestation.

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Extra ocular Muscles: OriginSuperior ObliqueLevator palpebrae superioris

Medial Rectus

Lateral Rectus

Superior Rectus

Inferior RectusInferior Oblique

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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

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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.

SPIRAL OF TILLAUX

5.5 mm

6.5 mm6.9 mm

7.7 mm

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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

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LEVATOR PALPEBRAE 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

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• NERVE SUPPLY- Upper division of occulomotor nerve.• ACTION- Elevation of upper eyelid.

• PtosisDrooping of upper eyelid.

VEDIO

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SUPERIOR RECTUS MUSCLE

• Origin-Superior part of common tendon of zinn.

• Insertion-inserted into sclera by flat tendinous insertion about 7.7 mm behind sclero-corneal

junction.• Nerve supply-superior

division of occulomotor nerve.

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Action of Superior Rectus• Primary action is elevation . . • Secondary action is adduction• Intorsion.

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INFERIOR RECTUS• Origin-inferior part of

common tendon of zinn• Insertion-in the sclera 6.5

mm behind sclero corneal junction.

• Nerve supply-inferior division occulomotor nerve.

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• ACTIONS- Primary depressor. Subsidiary actions are adduction and extorsion.

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MEDIAL RECTUS• Origin-annulus of zinn

and from optic nerve sheath.

• Insertion-in sclera 5.5mm behind sclero-corneal junction.

• Nerve supply-lower division of occulomotor nerve.

• ACTION- Primary adductor of the eye.

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LATERAL RECTUS• Origin-annulus of zinn.• Insertion-in the sclera 6.9mm behind sclerocorneal

junction.• Nerve supply-abducens nerve which enters the muscle

on the medial surface.

• ACTION- Primary abductor of eye.

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SUPERIOR OBLIQUE• Longest and thinnest intraorbital

muscle, the muscle ends before the 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.22

ACTIONS

Primary action-intorsion. Subsidiary actions-abduction and depression. Adducted position-depression.

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INFERIOR OBLIQUE• Origin-Anteromedial part 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.

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ACTIONS• Primary action-extorsion.• Subsidiary actions-elevations and abduction.• Causes elevation only in adducted position of

eyeball.

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Blood supply

EOM are supplied by the branches of ophthalmic artery.

1. Muscular branches2. 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

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• 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 rectusb. sup rectusc. LPSd. SO

• Medial muscular branches- a. medial rectusb. inferior rectusc. IO

• Lacrimal branch-LR and SR


Venous drainage of EOM • The venous drainage of the extraocular muscles is via the

superior and inferior orbital veins to ophthalmic veinsAnterior 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

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Nerve Supply of Extraocular Muscles

Superior division of oculomotor:- levator palpebrae superioris, superior rectusInferior division of oculomotor:- medial rectus, inferior oblique, inferior rectusTrochlear nerve - superior obliqueAbducent nerve - lateral rectus

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AL3SO4LR6

VEDIO

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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

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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)

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Tertiary position of gaze

• Positions assumed by the eyes when combination of vertical and horizontal movements occur.

• Dextroelevation• Dextrodepression• Levoelevation• levodepression

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Motion of 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.

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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

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Ductions Are tested by occluding one eye and asking the patient to

follow target in each direction of gazeDuctions consist of following-

1.adduction-MR

4.depression-

2.abduction-LR

6.Extorsion(IO)

3.Elevation(SR) 5.Intorsion

(SO)

OD


VersionTested 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)

VEDIO

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MUSCLE PRIMARY 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

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Superior Oblique

Inferior Oblique

Superior rectus

Inferior rectus

Medial rectus

Lateral rectus

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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

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• 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

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• 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

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• 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

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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.


Thankyou

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EXTRA OCULAR MUSCLES

Health & Medicine

Transcript of EXTRA OCULAR MUSCLES