extra ocular muscles
TRANSCRIPT
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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
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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.
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SPIRAL OF TILLAUX
5.5 mm
6.5 mm6.9 mm
7.7 mm
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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
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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.
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VEDIO
23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 14
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Dept. of Ophthalmology, JNMC, Belagavi
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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
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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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Dept. of Ophthalmology, JNMC, Belagavi 27
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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
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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
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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
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Dept. of Ophthalmology, JNMC, Belagavi 37
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)
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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.
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Thankyou
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