## **Core Concept**
The "Bull's Eye" lesion in the retina is a characteristic finding in certain toxicities, particularly those affecting the macula. This condition is often associated with damage to the retinal pigment epithelium (RPE) and the photoreceptors. The Bull's Eye maculopathy is named for its appearance, with a ring of retinal pigment epithelium atrophy around a central island of relatively spared retina.

## **Why the Correct Answer is Right**
Chloroquine and its derivative hydroxychloroquine are well-known to cause retinal toxicity, leading to a condition known as chloroquine retinopathy or maculopathy. This toxicity can result in a Bull's Eye appearance on fundoscopy due to the parafoveal retinal pigment epithelium atrophy. The mechanism involves the accumulation of the drug in the retina, leading to damage. The correct answer, therefore, involves a drug known for this side effect.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and does not provide a drug to assess for correctness.
- **Option B:** Similarly, this option lacks information to evaluate its accuracy in relation to Bull's Eye lesion.
- **Option D:** This option also does not specify a drug, making it impossible to judge its relevance to the Bull's Eye lesion.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that hydroxychloroquine and chloroquine retinal toxicity can be screened for by performing a visual field test (notably, the 10-2 visual field test) and by assessing the retinal appearance. The risk of toxicity increases with higher doses and longer duration of use. Regular ophthalmologic monitoring is recommended for patients on long-term therapy.

## **Correct Answer: C. Chloroquine.**