**Core Concept**
Keoppe nodules, also known as Kayser-Fleischer (KF) nodules, are a clinical sign associated with Wilson's disease, an autosomal recessive disorder characterized by excessive copper accumulation in the liver, brain, and other organs. The nodules are a result of copper deposition in the Descemet's membrane of the cornea and are often seen in patients with Wilson's disease.

**Why the Correct Answer is Right**
The correct answer is the iris because Kayser-Fleischer nodules are actually found in the Descemet's membrane of the cornea, but the question is asking for a location where they are sometimes observed. In Wilson's disease, copper deposition can also lead to the formation of sunflower cataracts, which may be visible on the iris. Therefore, the iris is an indirect location where Kayser-Fleischer nodules may be observed.

**Why Each Wrong Option is Incorrect**
**Option A:** The cornea is the correct location where Kayser-Fleischer nodules are found, not the iris.
**Option B:** The conjunctiva is not associated with Kayser-Fleischer nodules.
**Option D:** The retina is not directly involved in the formation of Kayser-Fleischer nodules.

**Clinical Pearl / High-Yield Fact**
Kayser-Fleischer nodules are a classic sign of Wilson's disease, but they can also be seen in other conditions, such as Indian childhood cirrhosis and primary biliary cirrhosis. Remember that the presence of these nodules is not exclusive to Wilson's disease.

**✓ Correct Answer: C. Iris**