COST COST 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 its thickness?
- Bowman's layer
- Descemet's membrane
- Stroma (Correct answer)
- Epithelium
Correct answer: Stroma
The corneal stroma, composed of regularly arranged collagen lamellae, accounts for about 90% of corneal thickness and is the primary determinant of corneal transparency.
Question 2: The aqueous humor is produced by which ocular structure?
- Choroid
- Ciliary body (Correct answer)
- Iris
- Trabecular meshwork
Correct answer: Ciliary body
The ciliary body's non-pigmented epithelium actively secretes aqueous humor, which fills the anterior and posterior chambers of the eye.
Question 3: What is the primary route by which aqueous humor drains from the eye to maintain intraocular pressure?
- Schlemm's canal via the trabecular meshwork (Correct answer)
- Nasolacrimal duct
- Uveoscleral pathway only
- Posterior vitreous chamber
Correct answer: Schlemm's canal via the trabecular meshwork
About 80–90% of aqueous outflow occurs through the trabecular meshwork into Schlemm's canal, then into the episcleral venous system.
Question 4: Which cranial nerve is responsible for the majority of sensory innervation to the cornea?
- Cranial nerve II (optic)
- Cranial nerve III (oculomotor)
- Cranial nerve V1 (ophthalmic branch of trigeminal) (Correct answer)
- Cranial nerve VII (facial)
Correct answer: Cranial nerve V1 (ophthalmic branch of trigeminal)
The nasociliary branch of CN V1 (ophthalmic division of the trigeminal nerve) provides the dense sensory innervation that makes the cornea one of the most sensitive tissues in the body.
Question 5: The fovea centralis, which provides the highest visual acuity, is located within which retinal region?
- Optic disc
- Peripheral retina
- Macula lutea (Correct answer)
- Ora serrata
Correct answer: Macula lutea
The fovea is a specialized depression within the macula lutea, densely packed with cone photoreceptors and devoid of rods, enabling maximum visual resolution.
Question 6: Which extraocular muscle is responsible for intorsion and depression of the eye when the eye is in the adducted position?
- Inferior rectus
- Superior oblique (Correct answer)
- Inferior oblique
- Superior rectus
Correct answer: Superior oblique
The superior oblique muscle, innervated by CN IV, primarily intorts the eye and depresses it when the eye is adducted, acting through the trochlea as a pulley.
COST COST Ocular Anatomy and Physiology 1
Which layer of the cornea is responsible for its transparency and makes up approximately 90% of its thickness?