**Core Concept**
Snowflake cataract is a type of nuclear cataract that results from the denaturation of crystallin proteins in the lens, leading to the formation of characteristic snowflake-like opacities. This process is often associated with aging and prolonged exposure to UV radiation.

**Why the Correct Answer is Right**
The correct answer is related to the pathogenesis of snowflake cataract, which involves the accumulation of advanced glycosylation end-products (AGEs) and the subsequent activation of proteases that lead to protein denaturation. The denatured proteins aggregate and form insoluble fibrils that accumulate in the lens, causing opacity. This process is accelerated by the presence of oxidative stress and the activation of polyol and hexosamine pathways.

**Why Each Wrong Option is Incorrect**
**Option A:** While diabetes mellitus can cause cataracts, it is more commonly associated with cortical cataracts.
**Option B:** Age-related macular degeneration is a separate condition that affects the retina, not the lens.
**Option C:** Glaucoma is a group of eye conditions that damage the optic nerve, but it is not directly related to the formation of snowflake cataracts.

**Clinical Pearl / High-Yield Fact**
Snowflake cataracts are often seen in patients with a history of prolonged UV exposure, and their presence can be an indicator of cumulative sun damage.

**Correct Answer: D. Denaturation of crystallin proteins due to accumulation of advanced glycosylation end-products.**