The document describes the extra-ocular muscles that control eye movement and pupil size. It discusses both the intrinsic muscles that control the lens and pupil, and the extrinsic muscles involved in eye movement. The six extrinsic muscles include the superior, inferior, medial, and lateral rectus muscles, and the superior and inferior oblique muscles. Each muscle is described in terms of its origin, insertion, nerve supply, and primary action. The document also covers ocular movements including versions, ductions, and vergences. Laws of ocular motility like Hering's law of equal innervation are also summarized.

1. Extra-Ocular Muscles
By/Mohamed Ahmed El –Shafie
Assistant Lecturer in ophthalmology department
KafrELShiekh University
1

2. ORBITAL MUSCLES
Extrinsic muscles of eyeball.
• Involved in movement of eyeball.
Intrinsic muscles
• Controls shape of lens and size of pupil.
2

3. 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 3

4. vedio
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5. Extrinsic Muscles
Involuntary Muscles
Superior Tarsal Muscle
Inferior Tarsal Muscle
Orbitalis
Voluntary Muscles
Levator Palpebrae Superioris
Superior Rectus
Inferior Rectus
Medial Rectus
Lateral Rectus
Superior Oblique
Inferior Rectus
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6. Embryology
• mesodermal origin,
• Perimuscular Connective tissues from neural crest
• development beginning at 3– weeks of gestation.
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7. Extra ocular Muscles: Origin
Superior ObliqueLevator palpebrae superioris
Medial Rectus
Lateral Rectus
Superior Rectus
Inferior Rectus
Inferior Oblique
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8. 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.

10. SPIRAL OF TILLAUX
5.5 mm
6.5 mm
6.9 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.
• Ptosis
Drooping of upper eyelid.

14. VEDIO
23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi 14

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15Dept. of Ophthalmology, JNMC, Belagavi

16. 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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17. Action of Superior Rectus
• Primary action is elevation . .
• Secondary action is adduction
• Intorsion.
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18. 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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19. • ACTIONS-
Primary depressor.
Subsidiary actions are
adduction and extorsion.
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20. 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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21. 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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22. SUPERIOR OBLIQUE
• Longest and 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.
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23. ACTIONS
 Primary action-intorsion.
 Subsidiary actions-abduction and depression.
 Adducted position-depression.
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24. 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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25. 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 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

27. Dept. of Ophthalmology, JNMC, Belagavi
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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

28. Dept. of Ophthalmology, JNMC, Belagavi
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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 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

29. 23rdJuly '15
Dept. of Ophthalmology, 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 rectus
Trochlear nerve - superior oblique
Abducent nerve - lateral rectus
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AL3SO4LR

30. 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 gaze
 Ductions consist of following-
1.adduction-MR
4.depression-
2.abduction-LR
6.Extorsion
(IO)
3.Elevation
(SR) 5.Intorsion
(SO)
OD

37. Dept. of Ophthalmology, JNMC, Belagavi
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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)

38. 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

43. 43
• 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

45. 23rd July '15 Dept. of Ophthalmology, JNMC, Belagavi
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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.
Dept. of Ophthalmology, JNMC, Belagavi 45

46. Thankyou

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