Anatomy of extraocular muscles and ocular motility
Angle of the medial and lateral walls of the orbit is 45°
so the optical axis forms approimately 23 °with both
medial &lateral walls.
The medial walls of the 2 orbits are parallel to each
Two oblique muscles:-
In addition levator palpebrae superioris also present
&it inserts into upper eye lid for elevating palpebral
The 4 rectii arises from fibrous ring (annulus of
zinn)around optic foramen.
Vertical recti(sup.&inf. Rectus ) run in line with orbital
axis & are inserted infront of equator.
They form an angle of 23° with visual axis.
Arises from upper part of annulus o zinn.
Below the attachment of levator M.
Continuous with attachment of med.,&lat. Recti
Pierces tenon’s capsule &it is inserted into sclera 7.7
mm from superior limbus.
Length 48 mm;width 9mm.
N.supply:-sup.divison of oculomotor N.
B.supply:-lat. Muscular branch of ophthalmic A.
Shortest of all recti
Arises from lower part of optic foramen.
Attached to sclera at 6.5 mm from inferior limbus
Lies b/w globe and inf.oblique.
Also attached to fascial sheath of lower lid.
Length 40mm;width 9mm
N.supply:-branch of inf divison of oculomotor N.
B.supply:-medial muscular branch of ophthalmic A.
Largest ocular M& stronger than lateral rectus.
Arise from medial & inferior sides of optic foramen
Passing along medial wall of orbit ;inserts 5.5mm from
Length 40mm;thicker than other EOM.
N.supply:-inf.divison of oculomotor N.
B.supply:-medial muscular branch of ophthalmic A.
Arises from annular tendon.
Pierces tenon’s capsule &inserts in sclera at 6.9 mm
from temporal limbus.
Length 48mm;2/3 of cross sectional area of MR.
N.supply:-Abducent N enters lR on its ocular
aspect,just post.to its mid point.
Spiral of tillaux
Imaginary line joining the insertions of the 4 recti and
is an important anatomical landmark when
The insertions are located progressively further away
from the limbus in a spiral pattern.
the medial rectus insertion is closest .
Superior rectus is farthest.
Obliques are inserted behind equator & form an angle
of 51° with visual axis.
Longest& thinnest EOM.
Arises from common origin at the apex of orbit;
superomedial to optic foramen.
Runs forward to trochlea(cartilaginous ring at
upper&inner angles of orbit)
After threading through this it becomes tendinous
It changes its direction completely and runs over the
globe under SR to attach above & lat, to posterior pole.
Ant.fibres of S.O tendon-intorsion
Post.fibres of S.O tendon-extorsion
N.supply:-Trochlear N(4) after dividing into 2-3
branches enters muscle superiorly.
B.supply:-superior muscular branch of ophthalmic A.
Only EOM not arising from apex of orbit
It arises anteriorly from lower & inner orbital walls
near lacrimal fossa.
Running below inf.rectus& attaches below&lat. to
post.pole of globe.
N.supply:-Inf.divison of oculomotor N.
B.supply:-Infraorbital &medial muscular branches of
Action of extraocular muscles
Rotation around centre of rotation
Centre of rotation lies 12/13 mm behind cornea.
3 types of rotation:
1. Rotation around fick vertical axis Z—side to side
2. “ “ fick horizontal axis X– up&down
3. “ “ fick antero posterior axis– torsion
Ductions – only one eye is open,the other covered/closed
tested by asking the pt. to follow a target in each direction
Types of ductions:-
Versions:-both eyes open,attempting to fixate a target
&moving in same direction.
Binocular ,simultaneous,conjugate movements in
Abduction of one eye accompanied by adduction of
other eye is called conjugate movements.
Types of versions:-
Dextro elevation&dextro depression
Laevo elevation& laevo depression
Torsional movements/righting reflexes:-
When you tilt head to maintain upright image.
Convergence– simultaneous adduction
Divergence– outward movement from convergent
Actions of EOM
ACTION PRIMARY SECONDARY TERTIARY
MR ADDUCTION ------ ---------
LR ABDUCTION ------ ---------
SR ELEVATION INTORSION ADDUCTION
IR DEPRESSION EXTORSION ADDUCTION
SO INTORSION DEPRESSION ABDUCTION
IO EXTORSION ELEVATION ABDUCTION
Both obliques have same tertiary action because
inserted behind the center of rotation,
pull post. pole of globe medially
when they contract ant.portion of eye so it causes
Both recti have same tertiary action bcz they inserted
anterior to centre of rotation
pull ant.portion of globe medially so it causes
Synergists:-ref.to muscles having same primary action
in same eye.
Ex:-sup.rectus & inf.oblique----elevators
Antagonists:-having opp.action in same eye
Yoke muscle(contralateral synergists):-
Ref. to pair of muscles (one from each eye) which
contract simultaneously during version movements.
Ex :-in dextroversion RLR &LMR
Contralateral antagonist:-pair of muscle (one from
each eye)having an opposite action.
Ex:-in dextroversion RLR & LLR
Diagnostic positions of gaze:-9
1 Primary position of gaze:-assumed by eyes when
fixating a distant object with head erect.
6 cardinal positions :- to test 12 EOM in their main
field of action
Laws of ocular motility
1. Hering’s law of equal innervation:- during any
conjugate movement equal & simultaneous
innervation flows to yoke muscles
2. Sherrington law of reciprocal innervation :-
inc.innervation to an EOM is accompanied by
reciprocal dec. in innervation to its antagonist.
Ex:-RMR & RLR
Supranuclear control of ocular
1. Saccadic system
2. Smooth pursuit system
3. Vergence system
4. Vestibular system
5. Optokinetic system
6. Position maintenance system
saccades are sudden,jerky,conjugate,movements
as the gaze shifts from one object to other.
Smooth pursuit eye movements:-
Tracking movements of eye as they follow moving
When the velocity of moving object inc. replaced by
small saccades(“catchup saccades”)
Allow focussing an object which moves away
Very slow disjugate movements
Vestibular eye movement:-
Effective in compensating for effects of head
movements in disturbing visual fixation
Through vestibular system
a movement following the moving scene , succeeded
by rapid saccade in opp.direction
Position maintenance system:-
Helps to maintain specific gaze by rapid micro
movements called “flicks” & slow micro movements