AOA Ocular Anatomy and Physiology 1 — Questions and Answers
Question 1: Which layer of the cornea is responsible for its transparency and makes up approximately 90% of corneal thickness?
- Epithelium
- Bowman's layer
- Stroma (Correct answer)
- Descemet's membrane
Correct answer: Stroma
The stroma constitutes about 90% of the cornea's thickness and is composed of regularly arranged collagen lamellae that contribute directly to corneal transparency.
Question 2: The aqueous humor is primarily produced by which ocular structure?
- Trabecular meshwork
- Ciliary body epithelium (Correct answer)
- Iris pigment epithelium
- Schlemm's canal
Correct answer: Ciliary body epithelium
The non-pigmented epithelium of the ciliary body actively secretes aqueous humor into the posterior chamber.
Question 3: The central retinal artery is a branch of which vessel?
- Internal carotid artery
- Ophthalmic artery (Correct answer)
- Anterior ciliary artery
- Posterior ciliary artery
Correct answer: Ophthalmic artery
The central retinal artery is a branch of the ophthalmic artery, which itself is the first branch of the internal carotid artery.
Question 4: Which photoreceptor type is responsible for scotopic (low-light) vision and is most densely concentrated in the peripheral retina?
- S-cones
- M-cones
- Rods (Correct answer)
- Intrinsically photosensitive retinal ganglion cells
Correct answer: Rods
Rods are highly sensitive photoreceptors that mediate scotopic vision and are densely distributed in the peripheral retina, outside the fovea.
Question 5: The fovea centralis is specialized for high-acuity vision primarily because it contains a high density of which cell type?
- Rods
- Cone photoreceptors (Correct answer)
- Horizontal cells
- Amacrine cells
Correct answer: Cone photoreceptors
The fovea has the highest density of cone photoreceptors and lacks rods, providing maximum visual acuity and color discrimination.
Question 6: Which extraocular muscle is responsible for intorsion of the eye when it is in the primary position?
- Superior rectus
- Inferior oblique
- Superior oblique (Correct answer)
- Medial rectus
Correct answer: Superior oblique
The superior oblique's primary action in the primary position is intorsion (incycloduction), with secondary actions of depression and abduction.
Question 7: The optic nerve is surrounded by an extension of which meningeal layer that forms the optic nerve sheath?
- Pia mater only
- Dura mater only
- All three meningeal layers (Correct answer)
- Arachnoid mater only
Correct answer: All three meningeal layers
The optic nerve is surrounded by all three meningeal layers—dura, arachnoid, and pia mater—which form the optic nerve sheaths and are continuous with the brain meninges.
AOA Ocular Anatomy and Physiology 1
Which layer of the cornea is responsible for its transparency and makes up approximately 90% of corneal thickness?