Anatomy and physiology of extraocular muscles.

1. Presentor :Dr. Uttara Bhat

2. Muscles of the orbit
Voluntary
Recti
Superior Rectus
Inferior Rectus
Lateral Rectus
Medial Rectus
Obliques
Superior
Oblique
Inferior
Oblique
Levator
palpebrae
superioris
Involuntary
Superior
Tarsal
Inferior
Tarsal
Orbitalis

3. RECTI MUSCLES
Origin
•The four recti muscles
originate from a common
tendinous ring( the annulus of
Zinn).
• Attached to the apex of the
orbit which bridges across the
superior orbital fissure.

4. Insertion
• Proceed forward and are inserted
infront of the equator of the
eyeball and behind the
sclerocorneal junction.
•The insertion of recti being not
equidistant from the limbus form
a spiral;
The spiral of Tillaux.
Medial Rectus = 5.5 mm
Inferior Rectus = 6.5 mm
Lateral Rectus = 6.9 mm
Superior Rectus = 7.7 mm

5. OBLIQUE MUSCLES
Superior Oblique
Origin
•Anatomical -Arises from the undersurface of the lesser wing
of sphenoid, above and medial to the optic foramen.
•Physiological- Tochlea.
Insertion
•The tendon of the muscle passes through the trochlea, turns
posterolaterally, passes under the SR muscle and fans out to
get inserted on the sclera.
Longest and the thinnest of all extraocular muscles(59.5mm)

6. Inferior Oblique
Origin
• Shallow depression on the orbital plate of maxilla lateral to the orifice
of NLD.
• Passes laterally and backwards, between IR muscle and the floor of
the orbit.
Insertion
• Lower and outer part of the sclera behind the equator, in
posterosuperior quadrant of eyeball.
Shortest extraocular muscle.( 37mm)

7. LEVATOR PALPEBRAE SUPERIORIS
• Origin
Inferior surface of lesser wing of sphenoid
• Insertion
Nerve supply
• Voluntary part- Superior division of
Occulomotor nerve
• Involuntary part- Sympathetic nervous
system
Action- Elevation of the upper eyelid.
Superior Lamina Inferior Lamina/ Muller’s
muscle
Skin of the upper eyelid
and anterior surface of
superior tarsal plate.
Upper margin of superior
tarsus and superior
conjunctival fornix.
Voluntary Involuntary

8. NERVE SUPPLY LR6SO4O3
All striated ocular muscles
are supplied by CN III (
Occulomotor Nerve), except
the Lateral Rectus and
Superior Oblique.
• Inferior division- MR, IR,
IO
• Superior division - SR
• Lateral Rectus – Abducens
Nerve ( CN VI )
• Superior Oblique-
Trochlear Nerve ( CN IV)

9. OPHTHALMIC ARTERY
MEDIAL
MUSCULAR
MR, IR,
IO
LATERAL
MUSCULAR
LR, SR, SO,
LPS
BLOOD SUPPLY OF EOMS
Veins- Correspond to the arteries and
empty into superior and inferior
ophthalmic veins and finally into the
cavernous sinus.
Anterior
Ciliary
Arteries
(7)

11. Orbital Fascia
Fascia Bulbi/
Tenon’s capsule
Fascial sheaths of
EOMs
Intermuscular
septa
Fascial
expansions of
EOMs

12. FASCIA BULBI/ TENON’S CAPSULE.
• Envelops globe from limbus to optic disc.
• Seperated from conjunctiva above – subconjunctival space
• Seperated from sclera below- episcleral space.
Anterior Tenon’s capsule is the subconjunctival membrane
that extends from the limbus to the level of penetration of
the rectus muscles.
Posterior Tenon’s capsule extends from the penetration of
the recti muscles to the optic nerve and thus separates the
orbital fat from the sclera.

14. FASCIAL SHEATHS OF EXTRAOCULAR MUSCLES
• Each extraocular muscle has an extracapsular (outside
Tenon’s capsule) and an
intracapsular part.
• The extracapsular part of each muscle is surrounded by a
fascial sheath (muscle capsule or muscle sleeve).
Form barrier between orbital fat and globe along with tenons
capsule.
INTERMUSCULAR SEPTA/MEMBRANE
• The sheaths of the four rectus muscles are joined to each
other by a fascial membrane called the intermuscular
septum.
• This membrane divides the orbital cavity and orbital fat into
a central and a peripheral part.

16. FASCIAL EXPANSIONS OF EXTRAOCULAR MUSCLES
• Check ligaments: Fascial expansions of lateral and medial rectus muscles
are strong and are attached to orbital tubercle on the zygomatic bone and
to the lacrimal bone, respectively.
These are also called lateral and medial check ligaments.
• Rectus muscle pulleys of connective tissue These are suspended from the
orbital walls through which the rectus muscles pass.
Modify the pull of rectus muscles.
• Expansion of superior rectus muscle is attached to the levator palpebrae
superioris. This attachment ensures synergic action of the two muscles.
• Expansion from the inferior rectus muscle is attached to the
capsulopalbebral fascia, a tissue analogous to levator aponeurosis in the
lower lid and the sheath of inferior oblique muscle.

17. Suspensory ligament of Lockwood
It is a thickened sling or hammock of fascial sheath extending from the
posterior lacrimal crest to the lateral orbital tubercle, on which rests the
eyeball.
Expansions from the muscular sheaths of the medial rectus, inferior oblique,
inferior rectus and lateral rectus muscles joined with the thickened inferior part
of Tenon’s capsule.
Superior transverse ligament of the Whitnall.
Thickened band of orbital fascia which extends from the trochlear pulley to the
lacrimal gland and its fossa.
It is formed by a condensation of the superior sheaths of the levator muscle.
It forms a true check ligament of the levator muscle.

19. PHYSIOLOGY OF EXTRAOCULAR MUSCLES
Basic Kinematics.
• Optical Axis- Passes from the fovea through the nodal
point, to the point of fixation.
• Anatomical Axis- Line passing from posterior pole to
the centre of the cornea.
• Angle kappa- Angle made by visual axis with the
anatomical axis. Usually 5° .

20. POSITIONS OF GAZE
Primary position of gaze
Position of eyes in binocular vision, when the head is 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.
All other ocular movements are initiated from this position.

21. Secondary positions of gaze
• Straight up ( Supraversion)
• Straight down (Infraversion)
• Right gaze ( Dextroversion)
• Left gaze ( Levoversion)

22. Tertiary Positions of gaze
These describe the positions assumed by the eyes, when
combination of horizontal and vertical movements occurs.
• Dextroelevation
• Dextrodepression
• Levoelevation
• Levodepression
Cardinal positions of gaze
Positions that allow examination of
each of the 12 EOMs of the 2 eyes in
the main field of action. 6 in number.

23. ACTIONS OF EOMS IN PRIMARY POSITION OF GAZE

24. FICK’S AXES
Describes three axes to analyze all movements of the globe around
the hypothetical centre of rotation (a fixed point, defined as
13.5mm behind the apex of cornea).
• X-Axis (horizontal) : rotation results in elevation and depression
• Y-Axis (Anteroposterior) Results torsional movements-Extorsion
and Intorsion.
• Z-Axis ( Vertical) : Rotation results in Abduction and Adduction.

25. Mechanics of Action of EOMs
1. Cross sectional area of the muscle.
• Horizontal recti- Max cross sectional area, since they
are the sole horizontal movers.
• Vertical recti- 75% and obliques- 50% size of horizontal
muscles.
• Antagonists are similar in size, thereby balancing
opposite forces.
2. Length of the muscle.
For normal amplitude of rotation (45°-50°) from primary
position, approx. 10mm change in muscle length required
in each direction.

26. 3. Arc of Contact
Distance on the scleral circumference between the
tangential point(T) and the centre of anatomic insertion(A)
of sclera. Represents lever arm in the mechanical system.
Power of muscle∝ Length of the muscle and arc of contact

27. 4.Muscle Plane.
Imaginary line passing through
• Origin of muscle (O)
• Centre of fixation (C)
• Anatomical insertion of muscle (A)
• Tangential Point (T)

28. RELATION OF MUSCLE PLANE OF SUPERIOR AND INFERIOR
RECTI WITH THE VISUAL LINE IN PRIMARY POSITION

29. RELATION OF MUSCLE PLANE OF SUPERIOR AND INFERIOR
OBLIQUES WITH THE VISUAL LINE IN PRIMARY POSITION

30. CLASSICAL CONCEPT OF ACTIONS OF EOMS
Horizontal recti Muscles
• Common muscle plane which is horizontal in position,
and coincides with the Z axis of the globe
• Pure horizontal movers around vertical Z axis and have
only primary action.

31. Position Action Axis
Primary Position Primary-
Elevation
X axis
Secondary-
Intorsion
Y axis
Tertiary-
Adduction
Z axis
SUPERIOR RECTUS
Position Action Axis
23° abduction Elevation optical axis and
muscle plane
coincide
67° adduction Intorsion Angle between
optical axis and
muscle plane 90°

33. Position Action Axis
Primary position Primary-
depression
Secondary-
Extorsion
Tertiary-
Adduction
X axis
Y axis
Z axis
23° abduction Depression optical axis and
muscle plane
coincide
67° adduction Extorsion Angle between
ms plane and
optical axis-
90°
INFEROR RECTUS

34. SUPERIOR OBLIQUE
Position Action Axis
Primary position Primary-
Intorsion
Secondary-
Depression
Tertiary-
Abduction
Y axis
X axis
Z axis
51° adduction Depression Optical axis and
muscle plane
coincide
39° abduction Intortion Angle between
muscle plane
and optical
axis- 90°

37. INFERIOR OBLIQUE
Position Action Axis
Primary Position Primary-
extorsion
Secondary-
elevation
Tertiary-
Abduction
Y axis
X axis
Z axis
51°adduction Elevation muscle plane
and optical axis
coincide
39° abduction Extorsion Angle between
muscle plane
and optical
axis- 90°

38. AGONISTS, SYNERGISTS ANTAGONISTS AND YOKE MUSCLES
 Agonist –a muscle whose contraction which produce specific
movement. Eg: right eye LR for right eye abduction.
▪ Synergists –muscle of the same eye that move the eye in the same
direction. Ex –right SR and right IO for right eye elevation.
▪ Antagonists –a pair of muscles in the same eye that moves the eye in
opposite direction. Eg –right LR and right MR.
▪ Yoke muscles ( contralateral synergists ) –pair of muscles, one in each
eye that produce conjugate ocular movement.
Eg –right LR and left MR in dextroversion.
 Contralateral antagonists/Antagonists of yoke muscles –Pair of muscles
one from each eye) having opposite action; eg.right LR and Left LR

40. FUNDAMENTAL LAWS GOVERNING OCULAR MOTILITY

41. HERING’S LAW OF EQUAL INNERVATION
States that an equal and simultaneous innervation
flows from the brain to a pair of muscles of both
eyes (yoke muscles) which contract simultaneously
in different binocular movements.

42. SHERRINGTON’S LAW OF RECIPROCAL INNERVATION
This law states that during ocular motility, an increased
flow of innervation to the contracting agonist muscle is
accompanied by a decreased flow of innervation to the
relaxing antagonist muscle.

43. OCULAR MOVEMENTS
1. Monocular movements(ductions)
• Adduction
• Abduction
• Supraduction/sursumduction
• Infraduction/ deosursumduction
• Incycloduction/ intorsion
• Excycloduction/extorsion

44. II. BINOCULAR MOVEMENTS
VERSIONS
SACCADES PURSUITS
POSITION
MAINTENANCE
MOVEMENTS
STABILIZATION
MOVEMENTS
VERGENCES

45. Versions
Binocular, simultaneous, conjugate movements in the same direc

46. Saccadic movements:
• Rapid, conjugate, jerky eye movements performed to bring image of an
object quickly back on the fovea.
• May be voluntary or involuntary.
• Alertness required for production of saccades.
• Once initiated, cannot be stopped or modified during course of
movement as they are preprogrammed.
• Eg. Optokinetic or vestibular nystagmus, during sleep (REM), command
random movements.

47. Pursuits/ Following movements
• Made when tracking/ following an object eg. Bird flying in the sky.
• Function of pursuit system is to match the eye velocity to target velocity.
Position maintenance movements
• Maintain specific gaze position by
• Rapid micromovemts- flicks
• Slow micromovements- drifts

48. Stabilization movements:
I. Dynamic movements.
• Transient inputs from the vestibular system during head movements.
II. Tonic movements
• Persist with head movements
• Gravity and other linear accelerations influence eye position by labyrinthine
reflexes from otoliths.
• Doll’s eye mechanism.

49. VERGENCES
Disconjugate, synchronous ,symmetric movements of the two eyes in
opposite direction.
CONVERGENCE –It is simultaneous and synchronous inward movement
of both eyes which results from contraction of medial recti
DIVERGENCE –It is simultaneous and asynchronous outward movement
of both eyes produced by contraction of lateral recti.
VERTICAL VERGENCE- Disconjugate vertical movements in opposite
direction
1. Positive vertical vergence/ Right supravergence/right
sursumvergence- Right eye moves upwards in relation to left
2 Negative vertical vergence/ Left supravergence/ left
sursumvergence- Left eye moves upwards in relation to left.

50. CYCLOVERGENCE
1. Incyclovergence-
Torsional disjugate
movement in which the
upper end of vertical
meridian tilts towards
nose
2. Excyclovergence- Upper
end of vertical meridian
of each eye tilts away
from nose.

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