anatomy of extraocular muscles

1. Dr.k.vanya

2. Bony orbit
 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
other.

4. Extraocularmusles(EOM):-6
 Four recti:-
 Superior rectus
 Inferior rectus
 Medial rectus
 Lateral rectus

5.  Two oblique muscles:-
 Superior oblique
 Inferior oblique
 In addition levator palpebrae superioris also present
&it inserts into upper eye lid for elevating palpebral
fissure.
 The 4 rectii arises from fibrous ring (annulus of
zinn)around optic foramen.

6.  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.

7. Superior rectus
 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.

8. Inferior rectus
 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.

9. Medial rectus
 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
nasal limbus.
 Length 40mm;thicker than other EOM.
 N.supply:-inf.divison of oculomotor N.
 B.supply:-medial muscular branch of ophthalmic A.


10. Lateral rectus
 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.

11. Spiral of tillaux
 Imaginary line joining the insertions of the 4 recti and
is an important anatomical landmark when
performing surgery.
 The insertions are located progressively further away
from the limbus in a spiral pattern.
 the medial rectus insertion is closest .
 Superior rectus is farthest.

13.  Obliques are inserted behind equator & form an angle
of 51° with visual axis.

14. Superior oblique
 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.

15.  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.

16. Inferior oblique
 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
ophtalmic A.

17. 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

19. Uniocular movements
 Ductions – only one eye is open,the other covered/closed
tested by asking the pt. to follow a target in each direction
of gaze.
 Types of ductions:-
1. Adduction
2. Abduction
3. Supraduction
4. Infraduction
5. Incycloduction
6. excycloduction

21. Binocular movements
 Versions:-both eyes open,attempting to fixate a target
&moving in same direction.
 Binocular ,simultaneous,conjugate movements in
same direction.
 Abduction of one eye accompanied by adduction of
other eye is called conjugate movements.

22. Types of versions:-
 Dextroversion&laevo version
 Elevation&depression
 Dextro elevation&dextro depression
 Laevo elevation& laevo depression

23.  Torsional movements/righting reflexes:-
 When you tilt head to maintain upright image.
 Vergences:-
binocular,simultaneous,disjugate/disjunctive
movements (opp.direction)
 Convergence– simultaneous adduction
 Divergence– outward movement from convergent
position

24. Types of convergence
 Reflex ----tonic
 ----proximal
 ----fusional
 ----accommodative
 voluntary

25. 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

26.  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
abduction

27.  Both recti have same tertiary action bcz they inserted
anterior to centre of rotation
 pull ant.portion of globe medially so it causes
adduction

28.  Synergists:-ref.to muscles having same primary action
in same eye.
 Ex:-sup.rectus & inf.oblique----elevators
 inf.rectus&sup.oblique-----depressors
 Antagonists:-having opp.action in same eye
 Ex:-sup.&inf. Recti
 sup.&inf.oblique

29.  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

30. 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

31. 1. Dextroversion
2. Laevo version
3. Dextro elevation
4. Leavo elevation
5. Dextro depression
6. Laevo depression
 +2 Elevation
 Depression

33. Laws of ocular motility
1. Hering’s law of equal innervation:- during any
conjugate movement equal & simultaneous
innervation flows to yoke muscles

34. 2. Sherrington law of reciprocal innervation :-
 inc.innervation to an EOM is accompanied by
reciprocal dec. in innervation to its antagonist.
 Ex:-RMR & RLR

35. Supranuclear control of ocular
movements:-
1. Saccadic system
2. Smooth pursuit system
3. Vergence system
4. Vestibular system
5. Optokinetic system
6. Position maintenance system

36.  Saccadic system:-
saccades are sudden,jerky,conjugate,movements
as the gaze shifts from one object to other.
 voluntary(normal)
 invoiuntary(peripheral,auditory,visual
stimuli)

37.  Smooth pursuit eye movements:-
 Tracking movements of eye as they follow moving
object
 Voluntary movements
 When the velocity of moving object inc. replaced by
small saccades(“catchup saccades”)

38.  Vergence movement:
 Allow focussing an object which moves away
from/towards observer.
 Very slow disjugate movements

39.  Vestibular eye movement:-
 Effective in compensating for effects of head
movements in disturbing visual fixation
 Through vestibular system

40.  Optokinetic 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
called “drifts”.

41. Bibilography
 Adler’s physiology of eye -11th edition
 Wolff’s anatomy of eye -8th edition
 Parson’s disease of eye-21st edition
 Jack.j.kanski brad bowlingclinical ophthalmology -
7th edition
 A.k.Khurana comprehensive ophthalmology -
5th edition