AOA Ocular Anatomy and Physiology 2 — Questions and Answers
Question 1: Intraocular pressure (IOP) is primarily regulated by the balance between aqueous humor production and outflow through which primary drainage pathway?
- Uveoscleral pathway
- Trabecular meshwork and Schlemm's canal (Correct answer)
- Vortex veins
- Suprachoroidal space
Correct answer: Trabecular meshwork and Schlemm's canal
Approximately 80–90% of aqueous outflow occurs through the trabecular meshwork into Schlemm's canal, making this the conventional pathway primarily responsible for IOP regulation.
Question 2: Which layer of the retina contains the cell bodies of the photoreceptors?
- Inner nuclear layer
- Outer nuclear layer (Correct answer)
- Ganglion cell layer
- Inner plexiform layer
Correct answer: Outer nuclear layer
The outer nuclear layer contains the cell bodies (nuclei) of the rod and cone photoreceptors.
Question 3: The ciliary muscle contraction during accommodation causes which change to the crystalline lens?
- The lens flattens due to increased zonular tension
- The lens becomes more convex as zonular tension decreases (Correct answer)
- The lens moves anteriorly without changing shape
- The lens diameter increases
Correct answer: The lens becomes more convex as zonular tension decreases
When the ciliary muscle contracts, it moves anteriorly and inward, releasing zonular tension and allowing the elastic lens to assume a more spherical (convex) shape, increasing its power for near focus.
Question 4: The macula lutea gets its yellow color from which pigments?
- Melanin and rhodopsin
- Lutein and zeaxanthin (Correct answer)
- Carotenoids and hemoglobin
- Lipofuscin and flavoproteins
Correct answer: Lutein and zeaxanthin
The macular pigment is composed of lutein and zeaxanthin, two xanthophyll carotenoids that absorb blue light and are thought to protect the macula from phototoxic damage.
Question 5: Which cranial nerve innervates the lateral rectus muscle?
- CN III (Oculomotor)
- CN IV (Trochlear)
- CN VI (Abducens) (Correct answer)
- CN V (Trigeminal)
Correct answer: CN VI (Abducens)
The abducens nerve (CN VI) exclusively innervates the lateral rectus muscle, which abducts the eye.
Question 6: The retinal pigment epithelium (RPE) performs all of the following functions EXCEPT:
- Phagocytosis of shed photoreceptor outer segments
- Production of aqueous humor (Correct answer)
- Vitamin A metabolism and transport
- Maintenance of the outer blood-retinal barrier
Correct answer: Production of aqueous humor
Aqueous humor is produced by the ciliary body epithelium, not the RPE; the RPE's roles include photoreceptor outer segment phagocytosis, vitamin A cycling, and forming the outer blood-retinal barrier.
Question 7: The vitreous humor is composed primarily of which substance?
- Hyaluronic acid and collagen fibrils (Correct answer)
- Albumin and globulins
- Phospholipids and glycoproteins
- Fibronectin and laminin
Correct answer: Hyaluronic acid and collagen fibrils
The vitreous is approximately 99% water, with the structural framework provided by a network of hyaluronic acid (providing viscosity) and collagen fibrils (type II and IX).
AOA Ocular Anatomy and Physiology 2
Intraocular pressure (IOP) is primarily regulated by the balance between aqueous humor production and outflow through which primary drainage pathway?