**Question:** Snow blindness is caused by -

A. Light exposure
B. Dehydration
C. Vitamin A deficiency
D. Iritis

**Core Concept:** Snow blindness, also known as photokeratitis or icy winds, is a temporary ocular inflammation caused by intense ultraviolet (UV) radiation exposure. It primarily affects the cornea and conjunctiva.

**Why the Correct Answer is Right:** Snow blindness results from exposure to intense UV radiation, specifically UVB, during prolonged stay in high altitudes or under direct sunlight without proper eye protection. When UVB rays penetrate the cornea, it causes inflammation and pain, leading to symptoms like photophobia, redness, and blurred vision.

**Why Each Wrong Option is Incorrect:**

A. Light exposure (Correct, but not the primary cause)
B. Dehydration (Irrelevant; snow blindness is caused by UV radiation, not dehydration)
C. Vitamin A deficiency (Irrelevant; snow blindness is not directly linked to vitamin A status)
D. Iritis (Irrelevant; snow blindness affects the cornea and conjunctiva, not the iris)

**Clinical Pearl:** To prevent snow blindness, it is crucial to wear appropriate UV-protective eyewear like sunglasses or goggles when exposed to intense sunlight for prolonged periods.

**Correct Answer:** D. Iritis (Irrelevant; snow blindness affects the cornea and conjunctiva, not the iris)

In the context of the question, option D is incorrect because snow blindness primarily affects the cornea and conjunctiva due to intense ultraviolet (UV) radiation exposure, not the iris. The term "iritis" typically refers to inflammation of the iris, so this option is irrelevant to snow blindness. Using appropriate eye protection, such as sunglasses or goggles, is essential to prevent snow blindness.