Practice 80 high-yield MCQs on Orbit and Extraocular Muscles Includes answers with short explanations for NEET PG, NEXT, AIIMS, and MRCSEd exam preparation.”
Orbit – General Anatomy
1. Shape of the orbit is:
A. Cone
B. Quadrilateral pyramid ✅
C. Sphere
D. Ellipsoid
Exp: Orbit resembles a 4-sided pyramid with apex posteriorly.
2. Average orbital volume in adults:
A. 25 ml
B. 30 ml ✅
C. 35 ml
D. 40 ml
Exp: Orbital cavity volume ≈ 30 ml.
3. Volume occupied by eyeball within orbit:
A. One-third ✅
B. One-half
C. Two-thirds
D. Three-fourths
Exp: Eyeball ~7 ml, orbit ~30 ml.
4. Roof of orbit is formed mainly by:
A. Frontal bone ✅
B. Sphenoid greater wing
C. Maxilla
D. Zygomatic
Exp: Orbital roof = frontal bone + lesser sphenoid.
5. Floor of orbit formed mainly by:
A. Maxilla ✅
B. Frontal bone
C. Ethmoid
D. Lacrimal
Exp: Orbital floor = maxilla + zygomatic + palatine.
Orbital Walls
6. Medial wall of orbit includes:
A. Maxilla
B. Lacrimal, ethmoid, sphenoid ✅
C. Zygomatic
D. Frontal
Exp: Medial wall very thin (lamina papyracea).
7. Strongest orbital wall:
A. Medial
B. Lateral ✅
C. Roof
D. Floor
Exp: Lateral wall thick and strong.
8. Weakest orbital wall:
A. Floor ✅
B. Roof
C. Lateral
D. Medial
Exp: Floor thin → blow-out fracture.
9. Apex of orbit contains:
A. Optic canal ✅
B. Lacrimal gland
C. Supraorbital notch
D. Nasolacrimal duct
Exp: Optic nerve and ophthalmic artery pass through canal.
10. Orbital margin formed by:
A. Maxilla, frontal, zygomatic ✅
B. Ethmoid, sphenoid, lacrimal
C. Nasal, palatine, temporal
D. Only sphenoid
Exp: Orbital rim formed by frontal, zygomatic, maxilla.
Extraocular Muscles – Basics
11. Total extraocular muscles:
A. 4
B. 6 ✅
C. 7
D. 8
Exp: 4 recti + 2 obliques.
12. Recti muscles arise from:
A. Sphenoid lesser wing
B. Common tendinous ring (annulus of Zinn) ✅
C. Orbital rim
D. Lacrimal fossa
Exp: Annulus of Zinn surrounds optic canal.
13. Superior oblique arises from:
A. Orbital roof (sphenoid) ✅
B. Annulus of Zinn
C. Maxilla
D. Frontal bone
Exp: Arises from sphenoid, passes through trochlea.
14. Inferior oblique arises from:
A. Orbital floor (maxilla) ✅
B. Annulus of Zinn
C. Lacrimal bone
D. Sphenoid
Exp: Origin from anterior orbital floor.
15. Levator palpebrae superioris arises from:
A. Annulus of Zinn
B. Lesser wing of sphenoid ✅
C. Orbital roof
D. Zygomatic
Exp: LPS arises near optic canal.
16. Primary action of medial rectus:
A. Abduction
B. Adduction ✅
C. Elevation
D. Depression
Exp: MR → adduction.
17. Primary action of lateral rectus:
A. Adduction
B. Abduction ✅
C. Elevation
D. Depression
Exp: LR → abduction.
18. Primary action of superior rectus:
A. Elevation ✅
B. Depression
C. Intorsion
D. Abduction
Exp: SR elevates eye.
19. Secondary actions of superior rectus include:
A. Adduction + intorsion ✅
B. Abduction + extorsion
C. Depression + abduction
D. Adduction only
Exp: SR = elevation + adduction + intorsion.
20. Primary action of inferior rectus:
A. Depression ✅
B. Elevation
C. Intorsion
D. Adduction
Exp: IR depresses eye.
21. Primary action of superior oblique:
A. Intorsion ✅
B. Extorsion
C. Elevation
D. Depression
Exp: SO intorts the eye.
22. Secondary actions of superior oblique:
A. Abduction + depression ✅
B. Adduction + elevation
C. Intorsion + elevation
D. Abduction + elevation
Exp: SO = intorsion + depression + abduction.
23. Primary action of inferior oblique:
A. Extorsion ✅
B. Intorsion
C. Depression
D. Elevation
Exp: IO extorts the eye.
24. Secondary actions of inferior oblique:
A. Elevation + abduction ✅
B. Depression + adduction
C. Intorsion + abduction
D. Depression only
Exp: IO = extorsion + elevation + abduction.
25. Only muscle arising from anterior orbit:
A. Superior rectus
B. Inferior oblique ✅
C. Medial rectus
D. Levator palpebrae
Exp: IO arises from anterior orbital floor.
Nerve Supply of Muscles
26. Lateral rectus supplied by:
A. Oculomotor
B. Abducens ✅
C. Trochlear
D. Trigeminal
Exp: LR → VI nerve.
27. Superior oblique supplied by:
A. Oculomotor
B. Trochlear ✅
C. Abducens
D. Trigeminal
Exp: SO → IV nerve.
28. All other extraocular muscles supplied by:
A. Trochlear
B. Abducens
C. Oculomotor ✅
D. Trigeminal
Exp: Oculomotor → MR, SR, IR, IO, LPS.
29. Mnemonic “LR6 SO4, rest 3” indicates:
A. LR → CN VI, SO → CN IV, rest → CN III ✅
B. LR → CN IV, SO → CN VI
C. LR → CN III, SO → CN VI
D. LR → CN V, SO → CN IV
Exp: Helps recall innervation.
30. Levator palpebrae superioris innervation:
A. Abducens
B. Trochlear
C. Oculomotor ✅
D. Trigeminal
Exp: Supplied by superior division of CN III.
31. Paralysis of lateral rectus causes:
A. Medial squint (esotropia) ✅
B. Lateral squint
C. Hypertropia
D. Hypotropia
Exp: Eye pulled medially.
32. Paralysis of superior oblique causes:
A. Vertical diplopia ✅
B. Horizontal diplopia
C. Loss of abduction
D. Ptosis
Exp: SO palsy → vertical diplopia.
33. Trochlear nerve palsy leads to:
A. Inability to intort ✅
B. Inability to abduct
C. Inability to adduct
D. Inability to elevate
Exp: SO palsy → intorsion loss.
34. Abducens nerve palsy leads to:
A. Medial deviation of eye ✅
B. Lateral deviation
C. Vertical deviation
D. Ptosis
Exp: LR palsy → esotropia.
35. Oculomotor palsy leads to all EXCEPT:
A. Ptosis
B. Dilated pupil
C. Abduction of eye ✅
D. Loss of elevation
Exp: CN III palsy leaves LR & SO intact → eye abducted & depressed.
Extraocular Movements
36. In primary position, all recti pull eye towards:
A. Posterior pole ✅
B. Anterior pole
C. Lateral side
D. Medial side
Exp: Recti contract to pull eye backward.
37. Yoke muscles are:
A. Same eye synergists
B. Contralateral synergists ✅
C. Antagonists
D. Ipsilateral agonists
Exp: Yoke muscles coordinate binocular movements.
38. Sherrington’s law relates to:
A. Reciprocal innervation of agonist/antagonist ✅
B. Yoke muscles
C. Hering’s law
D. Accommodation
Exp: One contracts, antagonist relaxes.
39. Hering’s law relates to:
A. Equal innervation of yoke muscles ✅
B. Reciprocal innervation
C. Retinal correspondence
D. Accommodation
Exp: Both eyes receive equal innervation.
40. Bielschowsky head tilt test is used in diagnosis of:
A. Superior oblique palsy ✅
B. Lateral rectus palsy
C. Oculomotor palsy
D. Ptosis
Exp: Head tilt exaggerates SO weakness.
Orbit – Foramina & Openings
41. Optic canal transmits:
A. Optic nerve + ophthalmic artery ✅
B. Optic nerve + central retinal vein
C. Oculomotor nerve + ophthalmic artery
D. Trochlear nerve + ophthalmic vein
Exp: Only optic nerve & ophthalmic artery.
42. Superior orbital fissure lies between:
A. Greater & lesser wings of sphenoid ✅
B. Frontal & maxilla
C. Zygomatic & sphenoid
D. Ethmoid & lacrimal
Exp: SOF between greater and lesser sphenoid.
43. Structures passing through superior orbital fissure include all EXCEPT:
A. Oculomotor nerve
B. Trochlear nerve
C. Maxillary nerve ✅
D. Abducens nerve
Exp: Maxillary nerve passes via foramen rotundum, not SOF.
44. Inferior orbital fissure connects orbit with:
A. Pterygopalatine & infratemporal fossae ✅
B. Middle cranial fossa
C. Posterior cranial fossa
D. Anterior cranial fossa
Exp: IOF opens into pterygopalatine and infratemporal fossa.
45. Lacrimal fossa is located in:
A. Frontal bone ✅
B. Maxilla
C. Lacrimal bone
D. Zygomatic
Exp: Lacrimal gland lies in frontal bone fossa.
Extraocular Muscles – Advanced Actions
46. Pure depressor of eye in abducted position:
A. Superior rectus
B. Inferior rectus ✅
C. Superior oblique
D. Inferior oblique
Exp: IR is pure depressor when eye abducted.
47. Pure depressor of eye in adducted position:
A. Inferior rectus
B. Superior oblique ✅
C. Superior rectus
D. Inferior oblique
Exp: SO depresses adducted eye.
48. Pure elevator of eye in abducted position:
A. Superior rectus ✅
B. Inferior rectus
C. Inferior oblique
D. Superior oblique
Exp: SR elevates abducted eye.
49. Pure elevator of eye in adducted position:
A. Superior rectus
B. Inferior oblique ✅
C. Inferior rectus
D. Superior oblique
Exp: IO elevates adducted eye.
50. Which muscle causes abduction in adducted position?
A. Superior oblique ✅
B. Inferior rectus
C. Inferior oblique
D. Superior rectus
Exp: SO abducts adducted eye.
Levator Palpebrae & Eyelid Muscles
51. Levator palpebrae superioris inserts into:
A. Upper tarsal plate ✅
B. Lower tarsal plate
C. Medial canthus
D. Orbital septum
Exp: Inserts into upper eyelid.
52. Accessory elevator of upper lid:
A. Muller’s muscle ✅
B. Inferior rectus
C. Superior rectus
D. Orbicularis
Exp: Sympathetic innervation.
53. Muller’s muscle innervation:
A. Parasympathetic
B. Sympathetic ✅
C. Oculomotor
D. Trochlear
Exp: Sympathetic supply from SCG.
54. Paralysis of levator palpebrae superioris →
A. Complete ptosis ✅
B. Partial ptosis
C. Lid retraction
D. Diplopia
Exp: CN III palsy causes complete ptosis.
55. Paralysis of Muller’s muscle →
A. Partial ptosis ✅
B. Complete ptosis
C. Lid lag
D. Blepharospasm
Exp: Sympathetic palsy = mild ptosis (Horner’s).
Clinical – Nerve Palsies
56. Oculomotor palsy features:
A. Ptosis, dilated pupil, eye down & out ✅
B. Eye abducted only
C. Eye intorted
D. Lid lag only
Exp: CN III palsy = “down and out” eye.
57. Trochlear palsy hallmark:
A. Vertical diplopia ✅
B. Horizontal diplopia
C. Convergent strabismus
D. Ptosis
Exp: SO palsy → vertical diplopia.
58. Abducens palsy hallmark:
A. Esotropia ✅
B. Exotropia
C. Hypertropia
D. Hypotropia
Exp: LR palsy → medial deviation.
59. Which nerve palsy worsens on looking down stairs?
A. Oculomotor
B. Trochlear ✅
C. Abducens
D. Trigeminal
Exp: SO palsy → difficulty in downgaze.
60. Isolated pupil involvement is most typical of:
A. Oculomotor nerve palsy ✅
B. Trochlear palsy
C. Abducens palsy
D. Horner’s syndrome
Exp: CN III palsy → dilated fixed pupil.
Eye Movements – Clinical Testing
61. To test superior rectus, ask patient to look:
A. Laterally then up ✅
B. Medially then up
C. Straight up
D. Downward
Exp: SR tested in abduction.
62. To test inferior rectus, ask patient to look:
A. Laterally then down ✅
B. Medially then down
C. Straight down
D. Upward
Exp: IR tested in abduction.
63. To test superior oblique, ask patient to look:
A. Medially then down ✅
B. Laterally then down
C. Straight down
D. Medially then up
Exp: SO tested in adduction.
64. To test inferior oblique, ask patient to look:
A. Medially then up ✅
B. Laterally then up
C. Straight up
D. Downward
Exp: IO tested in adduction.
65. Cover test is used for detecting:
A. Latent strabismus (heterophoria) ✅
B. Manifest strabismus
C. Diplopia
D. Ptosis
Exp: Cover test picks up phorias.
Orbit – Applied/Clinical
66. Commonest orbital wall fracture:
A. Floor (blow-out fracture) ✅
B. Roof
C. Lateral
D. Medial
Exp: Floor thin → blow-out in trauma.
67. In blow-out fracture, which muscle is entrapped?
A. Inferior rectus ✅
B. Superior rectus
C. Lateral rectus
D. Superior oblique
Exp: IR trapped in floor fracture.
68. Orbital cellulitis most dangerous complication:
A. Ptosis
B. Cavernous sinus thrombosis ✅
C. Conjunctivitis
D. Blepharitis
Exp: Via ophthalmic vein spread.
69. Proptosis refers to:
A. Forward displacement of eyeball ✅
B. Backward displacement
C. Medial displacement
D. Downward displacement
Exp: Protrusion of eyeball anteriorly.
70. Exophthalmometer measures:
A. Degree of proptosis ✅
B. Visual acuity
C. Intraocular pressure
D. Pupillary reflex
Exp: Hertel’s exophthalmometer.
Miscellaneous
71. Whitnall’s ligament supports:
A. Levator palpebrae superioris ✅
B. Superior rectus
C. Inferior rectus
D. Lateral rectus
Exp: Whitnall’s ligament acts as pulley for LPS.
72. Check ligament of medial rectus attached to:
A. Lacrimal crest ✅
B. Zygomatic bone
C. Frontal bone
D. Maxilla
Exp: Restricts excessive abduction.
73. Check ligament of lateral rectus attached to:
A. Zygomatic bone ✅
B. Lacrimal crest
C. Maxilla
D. Frontal
Exp: Restricts excessive adduction.
74. Lockwood’s ligament suspends:
A. Globe (inferior suspensory ligament) ✅
B. Levator muscle
C. Superior rectus
D. Lateral rectus
Exp: Lockwood’s ligament suspends globe.
75. Annulus of Zinn surrounds:
A. Optic canal ✅
B. Inferior orbital fissure
C. Supraorbital notch
D. Lacrimal fossa
Exp: Common origin of recti muscles.
76. Orbital septum functions to:
A. Prevent orbital fat prolapse ✅
B. Assist ocular motility
C. Maintain corneal transparency
D. Anchor lens
Exp: Fibrous sheet prevents fat prolapse.
77. Main stabilizers of globe in orbit:
A. Tenon’s capsule + check ligaments ✅
B. Recti muscles only
C. Oblique muscles
D. Orbital septum
Exp: Suspensory system maintains position.
78. Orbital axis vs visual axis:
A. Same direction
B. Differ by 23° ✅
C. Differ by 45°
D. Parallel
Exp: Orbital axis diverges 23° from visual axis.
79. Angle between medial walls of two orbits:
A. 30°
B. 45° ✅
C. 60°
D. 75°
Exp: Medial walls parallel, lateral walls diverge ~45°.
80. Angle between lateral walls of two orbits:
A. 30°
B. 45°
C. 90° ✅
D. 120°
Exp: Two lateral walls form ~90° angle.