Sunflower cataract is due to deposition of:

**Core Concept**
Sunflower cataract is a type of cataract that occurs due to the deposition of a specific substance within the lens of the eye. This condition is associated with a metabolic disorder that affects the lens and leads to the accumulation of a particular compound.

**Why the Correct Answer is Right**
Sunflower cataract is caused by the deposition of cholesterol within the lens of the eye. This occurs in conditions where there is an abnormality in lipid metabolism, leading to the accumulation of cholesterol in the lens. Cholesterol deposition can cause the lens to become cloudy, resulting in vision impairment. The condition is often seen in patients with hyperlipidemia or other metabolic disorders that affect lipid metabolism.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the deposition of calcium is associated with a different type of cataract, known as a snowflake cataract.
* **Option B:** This option is incorrect because the deposition of amyloid is associated with a different type of cataract, known as a lamellar cataract.
* **Option D:** This option is incorrect because the deposition of melanin is associated with a different type of cataract, known as a posterior subcapsular cataract.

**Clinical Pearl / High-Yield Fact**
Sunflower cataract is often seen in patients with hyperlipidemia, and it is associated with a poor prognosis if left untreated.

**Correct Answer: C. Cholesterol.**