NBEO Ocular Anatomy & Physiology 2

Question 1

What are rods and cones?

Accepted Answer

Photoreceptor cells in the retina: rods detect dim light (scotopic vision) and cones detect color and detail (photopic vision)

Answer

Rods (120 million, peripheral retina) provide night vision and motion detection. Cones (6 million, concentrated in the macula) provide color vision and fine detail in bright light.

Question 2

What is the vitreous humor?

Accepted Answer

A clear gel filling the posterior cavity of the eye that maintains the eye's shape and holds the retina in place

Answer

The vitreous is a transparent gel (99% water with collagen and hyaluronic acid) that maintains the globe's shape, transmits light to the retina, and provides metabolic support. With age, it liquefies and can cause floaters.

Question 3

What is the tear film and what are its layers?

Accepted Answer

A three-layer film (lipid, aqueous, mucin) covering the cornea that provides lubrication, nutrition, and protection

Answer

The tear film has three functional components: the outer lipid layer (prevents evaporation), the middle aqueous layer (provides nutrition and defense), and the inner mucin layer (helps tears adhere to the corneal surface).

Question 4

What is the pupillary light reflex?

Accepted Answer

The automatic constriction of the pupil in response to increased light intensity, mediated by the parasympathetic nervous system

Answer

The pupillary light reflex constricts both pupils (direct and consensual response) when light stimulates retinal photoreceptors, controlled by the parasympathetic pathway through the oculomotor nerve (CN III).

Question 5

What is accommodation?

Accepted Answer

The ability of the eye to change the shape of the crystalline lens to focus on objects at different distances

Answer

Accommodation involves ciliary muscle contraction releasing zonular tension, allowing the elastic lens to become more convex for near focus. This ability decreases with age (presbyopia) as the lens loses flexibility.

NBEO - National Board of Examiners in Optometry Practice Test

NBEO - National Board of Examiners in Optometry Practice Test

NBEO Ocular Anatomy & Physiology 2