**Core Concept**
Toxic retinopathy, also known as retinal toxicity, is a condition caused by exposure to certain substances that damage the retina, leading to visual impairment. The bull's eye retinal lesion is a characteristic feature of this condition, characterized by a ring-shaped area of retinal degeneration.

**Why the Correct Answer is Right**
The bull's eye retinal lesion is typically seen in toxic retinopathy due to chloroquine or hydroxychloroquine, which are antimalarial drugs used to treat autoimmune diseases such as lupus and rheumatoid arthritis. These drugs cause damage to the retina by accumulating in the retinal pigment epithelium and inducing apoptosis of retinal pigment epithelial cells. The resulting retinal degeneration creates a characteristic "bull's eye" appearance due to the preserved retinal pigment epithelium in the central macula.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a particular substance known to cause toxic retinopathy. While many substances can cause retinal toxicity, only chloroquine and hydroxychloroquine are commonly associated with the bull's eye retinal lesion.
* **Option B:** This option is incorrect because it does not accurately describe the mechanism by which toxic retinopathy occurs. While certain substances can accumulate in the retina, the bull's eye retinal lesion is specifically associated with chloroquine and hydroxychloroquine.
* **Option C:** This option is incorrect because it does not accurately describe the appearance of the retinal lesion. The bull's eye retinal lesion is characterized by a ring-shaped area of retinal degeneration, not a patchy or diffuse appearance.

**Clinical Pearl / High-Yield Fact**
To remember the association between chloroquine and toxic retinopathy, recall that the "fish eye" lesion is a characteristic feature of this condition, which can be easily confused with the "bull's eye" lesion. However, the fish eye lesion is typically associated with other antimalarial drugs, not chloroquine.

**Correct Answer: C. Chloroquine.**