**Core Concept:** Bull's eye lesion in the macula is a characteristic ocular manifestation of retinal toxicity due to prolonged use of chloroquine and hydroxychloroquine. These drugs are used to treat malaria and autoimmune disorders.

**Why the Correct Answer is Right:** The correct answer is (B) Hydroxychloroquine, as it is the most commonly used antimalarial drug and has a higher risk of retinal toxicity compared to other antimalarial drugs like chloroquine, quinine, sulfamethoxazole, and primaquine.

**Why Each Wrong Option is Incorrect:**

A. Chloroquine: Although chloroquine is another antimalarial drug, it is less commonly used than hydroxychloroquine and has a lower risk of retinal toxicity.

C. Quinine: Quinine is an antimalarial drug used for treating severe malaria and has a lower risk of retinal toxicity compared to hydroxychloroquine.

D. Sulfamethoxazole: Sulfamethoxazole is an antibiotic used for treating infections, not a drug affecting the retina.

E. Primaquine: Primaquine is an antimalarial drug, but it has a lower risk of retinal toxicity compared to hydroxychloroquine.

**Clinical Pearl:** Bull's eye lesion is a key feature of chloroquine and hydroxychloroquine-induced retinopathy, which occurs due to the accumulation of these drugs in the retinal pigment epithelium. This can lead to a reduction in visual acuity and even blindness if left untreated. Regular eye examinations are essential for early detection and management of this potentially reversible condition.

**Correct Answer:** B) Hydroxychloroquine