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14# Eye & Visual Pathway
1. The medial wall of the orbit is primarily separated from the ethmoidal air sinuses by which bone?
Lacrimal bone
Orbital plate of ethmoid
Body of sphenoid
Frontal bone
Explanation:
The orbital plate of the ethmoid (lamina papyracea) separates the orbit from the ethmoidal air sinuses.
2. Which structure passes through the optic canal?
Optic nerve and ophthalmic artery
Oculomotor nerve and superior ophthalmic vein
Maxillary nerve
Inferior ophthalmic vein
Explanation:
The optic canal transmits the optic nerve and ophthalmic artery only.
3. Which structure is transmitted through the inferior orbital fissure?
Optic nerve
Oculomotor nerve
Trochlear nerve
Zygomatic branch of maxillary nerve
Explanation:
The inferior orbital fissure transmits the maxillary nerve (zygomatic branch), inferior ophthalmic vein, and sympathetic fibers.
4. Increased intracranial pressure leads to papilledema because:
Optic nerve lacks dura mater
Central retinal artery is compressed
Subarachnoid space extends to the eyeball
Ophthalmic vein becomes obstructed
Explanation:
The optic nerve is surrounded by meninges, allowing raised CSF pressure to be transmitted to the optic disc.
5. Parasympathetic fibers to the sphincter pupillae synapse in which ganglion?
Ciliary ganglion
Pterygopalatine ganglion
Otic ganglion
Superior cervical ganglion
Explanation:
Preganglionic parasympathetic fibers from CN III synapse in the ciliary ganglion.
6. Which nerve carries sympathetic fibers to the dilator pupillae muscle?
Short ciliary nerves
Long ciliary nerves
Inferior division of CN III
Optic nerve
Explanation:
Long ciliary nerves (from nasociliary nerve) carry sympathetic fibers to the dilator pupillae.
7. Injury to which structure causes loss of corneal sensation?
Short ciliary nerves
Oculomotor nerve
Optic nerve
Long ciliary nerves
Explanation:
Long ciliary nerves provide sensory innervation to the cornea, making corneal injury very painful.
8. The central artery of the retina enters the eyeball at the level of the:
Macula lutea
Ora serrata
Optic disc
Fovea centralis
Explanation:
The central retinal artery pierces the optic disc to supply the retina.
9. Blockage of aqueous humor drainage leads directly to:
Cataract
Glaucoma
Retinal detachment
Macular degeneration
Explanation:
Obstruction of aqueous humor drainage through the canal of Schlemm causes glaucoma.
10. Which structure is avascular and receives nutrition by diffusion?
Cornea
Choroid
Retina
Iris
Explanation:
The cornea is avascular and is nourished by aqueous humor and tears.
11. Accommodation for near vision occurs due to:
Relaxation of ciliary muscle
Tightening of suspensory ligament
Flattening of the lens
Contraction of ciliary muscle
Explanation:
Ciliary muscle contraction relaxes zonular fibers, allowing the lens to become more convex.
12. The blind spot corresponds anatomically to the:
Macula lutea
Fovea centralis
Optic disc
Ora serrata
Explanation:
The optic disc lacks rods and cones and is therefore insensitive to light.
13. The lacrimal gland drains its secretion into which structure?
Lacrimal sac
Superior conjunctival fornix
Inferior nasal meatus
Nasolacrimal duct
Explanation:
The lacrimal gland opens into the superior fornix of the conjunctiva.
14. Which structure prevents tear overflow by sealing the eyelids?
Tarsal (meibomian) glands
Glands of Moll
Glands of Zeis
Lacrimal gland
Explanation:
Tarsal glands secrete oily material that seals the eyelids and prevents tear overflow.
15. Which extraocular muscle is supplied by the trochlear nerve?
Inferior oblique
Medial rectus
Inferior rectus
Superior oblique
Explanation:
The superior oblique muscle is innervated by CN IV (trochlear nerve).
16. Failure of abduction of the eye indicates damage to:
Abducent nerve
Oculomotor nerve
Trochlear nerve
Optic nerve
Explanation:
The lateral rectus muscle, responsible for abduction, is innervated by CN VI.
17. The optic nerve is unique because it is:
A peripheral nerve with Schwann cells
Derived from neural crest
A CNS tract derived from diencephalon
Unmyelinated throughout its course
Explanation:
CN II is a CNS tract formed as an evagination of the diencephalon.
18. Nasal retinal fibers decussate at the:
Optic tract
Optic chiasm
Optic radiation
Lateral geniculate body
Explanation:
Partial crossing of nasal retinal fibers occurs at the optic chiasm.
19. A lesion of the optic tract causes which visual field defect?
Ipsilateral monocular blindness
Bitemporal hemianopia
Central scotoma
Contralateral homonymous hemianopia
Explanation:
Each optic tract carries information from the contralateral visual field.
20. Compression of the optic chiasm by a pituitary adenoma results in:
Bitemporal hemianopia
Ipsilateral blindness
Central scotoma
Homonymous hemianopia
Explanation:
Compression of crossing nasal fibers causes loss of temporal visual fields in both eyes.