## **Core Concept**
The Kayser-Fleischer ring is a significant clinical finding associated with **Wilson's disease**, a genetic disorder leading to copper accumulation in various tissues, including the eyes. It involves the deposition of copper in a specific layer of the cornea.

## **Why the Correct Answer is Right**
The Kayser-Fleischer ring is characterized by the deposition of copper in the **Descemet's membrane** of the cornea. This membrane is a thin, acellular, and transparent layer of the cornea, which is part of the corneal structure. The deposition of copper in Descemet's membrane leads to the formation of the Kayser-Fleischer ring, which appears as a brownish or golden ring around the cornea.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because the Kayser-Fleischer ring is not primarily associated with the corneal epithelium.
- **Option B:** This option is incorrect as it does not specifically relate to Descemet's membrane.
- **Option C:** This option might relate to other structures but is not the correct location for the Kayser-Fleischer ring.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the Kayser-Fleischer ring is a diagnostic feature of Wilson's disease, and its presence is highly suggestive of the condition, especially in patients with neurological symptoms. However, its absence does not rule out Wilson's disease.

## **Correct Answer:** D. Descemet's membrane.