COST Ocular Anatomy and Physiology Flashcards

What is the approximate axial length of a typical emmetropic adult human eye?

Answer: 24 mm

The average emmetropic adult eye has an axial length of approximately 24 mm, which is a key biometric measurement used in IOL power calculations.

The vitreous humor occupies approximately what percentage of the total volume of the eye?

Answer: 60%

The vitreous humor fills the posterior segment and accounts for roughly 60% of the eye's total volume, providing structural support and a clear optical medium.

Which cells of the retina are primarily responsible for phototransduction in low-light (scotopic) conditions?

Answer: Rod cells

Rod photoreceptors contain rhodopsin and are exquisitely sensitive to dim light, making them the primary mediators of scotopic (night) vision.

The lens of the eye is held in place by which fibrous structure?

Answer: Zonules of Zinn (zonular fibers)

The zonules of Zinn (suspensory ligament of the lens) are fibrillin-rich fibers that connect the ciliary body to the lens equator, holding the lens in position.

Which layer of the retina lies immediately adjacent to the retinal pigment epithelium (RPE)?

Answer: Photoreceptor outer segments

The outer segments of photoreceptors (rods and cones) are in direct contact with the microvilli of the RPE, which phagocytoses shed outer segment discs.

Which structure forms the blood-ocular barrier on the outer retina side?

Answer: Bruch's membrane and RPE tight junctions

Tight junctions between RPE cells, along with Bruch's membrane, form the outer blood-retinal barrier, regulating transport between the choriocapillaris and the retina.