**Core Concept**
Metamorphopsia refers to a visual distortion or perception where shapes and objects appear to change, often in a way that is not related to their actual size or orientation. This phenomenon is commonly associated with retinal diseases, particularly age-related macular degeneration (AMD).

**Why the Correct Answer is Right**
Metamorphopsia occurs due to the disruption of the retinal photoreceptors, particularly in the macula, which is responsible for central vision and fine detail. The distortion is thought to result from the abnormal transmission of signals from the damaged photoreceptors to the visual cortex. In AMD, the accumulation of drusen (lipid deposits) and the formation of choroidal neovascularization can lead to metamorphopsia.

**Why Each Wrong Option is Incorrect**
**Option A:** Metamorphopsia is not a feature of cataracts, which primarily cause refractive errors and glare. Cataracts do not directly affect the retinal photoreceptors.
**Option B:** While glaucoma can cause visual field defects, it is not typically associated with metamorphopsia. Glaucoma primarily affects the optic nerve and can lead to progressive vision loss.
**Option C:** Metamorphopsia is not a characteristic of retinal detachment, which typically presents with sudden visual loss and a "curtain" or "shower" of floaters. Retinal detachment does not typically cause distortion of perceived shapes.

**Clinical Pearl / High-Yield Fact**
Metamorphopsia is a key symptom of AMD, and its presence can help differentiate this condition from other causes of visual distortion, such as cataracts or glaucoma.

**Correct Answer: D.**