COA Ocular Anatomy and Physiology 2 — Questions and Answers
Question 1: The crystalline lens is held in position by which structure?
- Vitreous humor pressure
- Zonular fibers (suspensory ligaments) (Correct answer)
- The posterior iris surface
- Corneal pressure
Correct answer: Zonular fibers (suspensory ligaments)
Zonular fibers connect the lens equator to the ciliary body, suspending the lens in the optical axis.
Question 2: Accommodation refers to which physiologic process?
- Adjustment of pupil size to light
- Changing lens curvature to focus at different distances (Correct answer)
- Adjustment of color perception in dim light
- Regulation of aqueous humor production
Correct answer: Changing lens curvature to focus at different distances
Accommodation changes the curvature of the crystalline lens by ciliary muscle contraction to focus objects at near.
Question 3: The vitreous humor consists primarily of:
- Lipids and plasma proteins
- Water with collagen fibrils and hyaluronic acid (Correct answer)
- Blood cells and serum
- Aqueous fluid identical to the anterior chamber
Correct answer: Water with collagen fibrils and hyaluronic acid
The vitreous is approximately 99% water supported by a framework of collagen fibrils and hyaluronic acid.
Question 4: Which photoreceptor cells are responsible for night (scotopic) vision?
- Cones
- Rods (Correct answer)
- Ganglion cells
- Müller cells
Correct answer: Rods
Rod photoreceptors are extremely sensitive to light and mediate vision under low-light (scotopic) conditions.
Question 5: Visual information travels from the retina via the optic nerve to which structure first?
- Primary visual cortex directly
- Lateral geniculate nucleus of the thalamus (Correct answer)
- Superior colliculus only
- Cerebellum
Correct answer: Lateral geniculate nucleus of the thalamus
Retinal ganglion cell axons project through the optic nerve to synapse in the lateral geniculate nucleus of the thalamus.
Question 6: Pupil constriction (miosis) and dilation (mydriasis) are controlled by which iris muscles?
- Sphincter muscle for miosis and dilator muscle for mydriasis (Correct answer)
- Ciliary muscle for both responses
- Choroidal smooth muscle
- Zonular fiber tension
Correct answer: Sphincter muscle for miosis and dilator muscle for mydriasis
The iris sphincter muscle (parasympathetic) constricts the pupil and the dilator muscle (sympathetic) dilates it.
COA Ocular Anatomy and Physiology 2
The crystalline lens is held in position by which structure?