Extraocular Muscles: Anatomy

1. EXTRA OCULAR
MUSCLES
ANATOMY
ORIGIN
INSERTION
NERVE SUPPLY
VASCULAR SUPPLY
FUNCTIONS

2. DISCUSSION AREAS
 EMBRYOLOGY
 ANATOMY
ORIGIN
COURSE
INSERTION
 NERVE SUPPLY
 BLOOD SUPPLY
 FUNCTIONS
 Clinical significances

3. EMBRYOLOGY
 EOMs (4 recti & 2 oblique) differentiate from the mesenchyme
in the region of developing eyeball (prechordal mesenchyme)
 Originally represented as a single mass of mesenchyme,
they later separate into distinct muscles

4.  appear approximately in the following sequences :
SR & LR → 5th week
MR & SO → 6th week
followed by IR & IO
 In the 8th week, all the motor nerves of the eye reaches
the EOMs.

5. EXTRA OCULAR MUSCLES
RECTUS MUSCLES
OBLIQUE
MUSCLES
 Muscles responsible for the controlled movements of
the eyeballs

6. RECTUS MUSCLES

7. ORIGIN
 a common tendinous ring ( the annulus of Zinn),
attached at the apex of orbit
 SR & MR lie closely attached to the dural sheath of
optic nerve at their origin

9. COURSE
 All the 4 recti run forward from their origin
 course is diverging ; however muscles converges
slightly in front of the equator to get inserted on the
sclera
 SR is separated from orbital roof by LPS muscle
 MR & LR follow the coresponding walls of orbit in
most of the parts in their course
 IR follow the orbit for only about half its length

11. INSERTION
 Rectus muscles do not form a circle concentric with the
limbus, rather form a spiral (the spiral of Tillaux)
Fuchs (1884)

12. Duane Retraction Syndrome
 A congenital ocular motility defect due to fibrous tightening
of lateral or medial rectus, or both
 Type I DRS : limitation of abduction
 Type II DRS : limitation of adduction
 Type III DRS : limitation of both adduction & abduction

14.  “Retraction of globe &
narrowing of palpebral fissure”
on attempted adduction

15. Strabismus fixus
 A rare condition characterized by bilateral fixation
of eyes in convergent position, due to fibrous
tightening of medial recti

16. Strabismus fixus

17. OBLIQUE MUSCLES

18. SUPERIOR OBLIQUE MUSCLES
 arise from the bone (body of Sphenoid)
above & medial to the optic foramen
ORIGIN

19. COURSE
 SO muscle moves forward between the roof &
medial wall of orbit to reach the trochlea, & turns
postero-laterally to get inserted onto the sclera
 TROCHLEA : a thick fibrous cartilaginous pulley
attached to spina trochlearis
on the under aspect of
frontal bone, at the
superomedial angle

20.  Reflected tendon of SO passes under the SR, &
fans out to get inserted on to the sclera

21. INSERTION
 width of Insertion line : about 11mm (7-18 mm)
Anterior end : lies 13.8mm behind the limbus
Posterior end : lies 18.8mm behind the limbus

22. fact…
Superior Oblique : longest & thinnest EOM
length of its direct part : 40mm
reflected tendon : 19.5 mm
TOTAL : 59.5 mm

23. Brown’s SO Tendon Sheath Syndrome
 A congenital ocular motility defect due to fibrous
tightening of SO tendon
 usually straight in primary position
 characterized by limitation of elevation of the eyes in
adduction (normal elevation in abduction)

24. INFERIOR OBLIQUE MUSCLES
 arises by a rounded tendon from a shallow
depression on the orbital plate of maxilla
 only muscle to originate from the front of orbit
ORIGIN
COURS
E
 runs between IR & floor of orbit,
laterally & backward

25. INSERTIO
N
 It is inserted by a short tendon (1 to 2 mm long) in
the lower & outer part of sclera behind the equator
 Near the insertion,
Inferior Vortex vein is in relation to
its posterior border
 shortest EOM → 37mm

26. Adhrence Syndromes
 a rare condition
 arises through abnormal fascial connections
between the reflections of Tenon’s Capsule along
the EOMs
 causing tethering of the globe

27.  occurs between :
IR& IO → limits elevation
LR & IO → limits adduction
SR & SO → limits depression

28. NERVE
SUPPLY

29.  supplied by Cranial Nerves (CN)
 CN III (oculomotor ) supplies
IR
SR
MR IO

30.  The branches from inferior division of CN III supply
IR, MR & IO
 The branch for SR originate from the upper division of CN
III

31.  SO → supplied by CN IV (Trochlear nerve)
the nerve divides into 3 or 4 branches
 LR → innervated by CN VI (Abducens nerve)

32. ABDUCENS
NERVE
TROCHLEAR
NERVE
SUPERIOR
DIVISION OF
3RD NERVE
INFERIOR
DIVISION OF
3RD NERVE

33.  Each axon innervates 3-10 muscle fibres
 Precise fine motor control and quick accurate
movement of EOMs

34. VASCULAR
SUPPLY

35. HEART
COMMON
CAROTID ARTERY
INTERNAL
CAROTID
ARTERY

36. OPHTHALMIC
ARTERY
MUSCULAR
ARTERY

38. MEDIAL
MUSCULAR
ARTERY
LATERAL
MUSCULAR
ARTERY
IR
MR
IO
SR
LR
SO
MR also receives a branch from lacrimal artery
IR & IO receives a branch from Infra orbital artery

39. FUNCTIONS

40. Some Terminologies…
AGONIST
 Any particular EOM producing a specific ocular movement
SYNERGISTS
 Two muscles moving an eye in the same direction
ANTAGONISTS
 Muscles having opposite actions in the same eye

41. YOKE MUSCLES
( CONTRALATERAL SYNERGISTS )
 A pair of muscles (one from each eye) which contract
simultaneously during version movements
CONTRALATERAL ANTAGONISTS
 A pair or muscles (one from each eye) having opposite
action

42. LAWS GOVERNING OCULAR MOTILITY
“ 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 ”
HERING’s LAW OF EQUAL INNERVATION

44. SHERRINGTON’S LAW OF
RECIPROCAL INNERVATION
“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”

45. SR IO
LR MR
IR SO
Marquez diagram
Right eye

47. Remember…
 All Superior muscles : Intort
 All Inferior muscles : Extort
 All Oblique muscles : Abduct

48. Clinical Significances

49. STRABISM
US
 A misalignment of the visual axes of the two
eyes
Classification
Pseudostrabismus / apparent squint
Heterophoria / latent squint
Heterotropia / manifest squint

50. TYPES OF
STRABISMU
S

51. ISOLATED MUSCLE
PARALYSIS
 most common : paralysis of LR & SO

52. LATERAL RECTUS PALSY
 due to palsy of 6th cranial nerve (abducens)
 results in convergent strabismus (Esotropia)
 primary symptom : Diplopia

53. SUPERIOR OBLIQUE
PALSY
 palsy of 4th nerve that innervates SO muscles
 common congenital anomaly associated is
Craniosynostosis
 causes a combination of vertical, horizontal &
torsional misalignment of the eyes
 head tilt / turn is commonly seen to allow better
alignment of the eyes; sometimes aiding relief in
diplopia

54. SUPERIOR OBLIQUE
PALSIES

55. DOUBLE ELEVATOR
PALSY
 caused by 3rd nerve nuclear lesion
 characterized by paresis of SR & IO muscle of the
involved eye
 restricted elevation of the eye
 patient with chin up position to maintain binocularity

57. DOUBLE DEPRESSOR
PALSY
 a rare condition
 paralysis of depressors
 monocular or unilateral restriction on down gaze

59. EXTERNAL
OPHTHALMOPLEGIA
 All EOMs are paralysed
 Intraocular muscles (sphincter pupillae, ciliary muscle)
are spared
 Due to lesions at the level of motor nuclei ; sparing the
Edinger-Westphal nucleus

60. TOTAL OPHTHALMOPLEGIA
 all EOMs including LPS and intraocular muscles
becomes paralysed
 results from combined paralysis of 3rd, 4th & 6th cranial
nerves
 common feature in case of Orbital apex syndrome &
Cavernous sinus thrombosis

61. DYSTHYROID OPHTHALMOPATHY
 also k/a Thyroid Eye Disease (TED) / Grave’s
Ophthalmopathy
 characterized by : Proptosis
Eyelid retraction
Corneal & conjunctival exposure
Conjunctival chemosis
 Chronic TED causes Hypertrophy & fibrosis of EOMs

62. Dysthyroid
Ophthalmopathy

63. REFRENC
ES
 Khurana A. K. , Khurana I.
Anatomy & Physiology of Eye
 Khurana A. K.
Comprehensive Ophthalmology
 Kanski J.J. , Bowling B.
Clinical Ophthalmology
 Previous Presentations
 Internet….etc

65. THANK YOU…..