**Core Concept**
Chalcosis is a type of cataract caused by chronic exposure to copper compounds, commonly seen in occupational settings. It results in a distinctive opacification of the lens with a characteristic "sunflower" appearance due to the deposition of copper salts within the lens fibers.

**Why the Correct Answer is Right**
In chalcosis, copper ions accumulate in the lens, leading to a yellowish or brownish opacification. The deposition forms a central, radiating pattern that resembles the petals of a sunflower when viewed under clinical examination. This unique morphological feature is known as sunflower cataract and is pathognomonic for copper toxicity. The mechanism involves copper-induced oxidative stress and protein denaturation within lens epithelial cells.

**Why Each Wrong Option is Incorrect**
Option B: Blue dot cataract is associated with chronic mercury exposure, not copper.
Option C: Snowflake cataract is caused by prolonged exposure to ultraviolet radiation, not copper.
Option D: Polychromatic lustre is a rare, non-specific cataract seen in certain metabolic disorders and not linked to copper toxicity.

**Clinical Pearl / High-Yield Fact**
Sunflower cataract is a hallmark of chalcosis and should be suspected in patients with occupational exposure to copper or copper-containing compounds. Always consider environmental toxins when evaluating unusual cataract types.

✓ Correct Answer: A. Sunflower cataract