**Core Concept**
Cotton wool spots are a type of retinal lesion characterized by fluffy, white patches on the retina, often indicative of retinal ischemia or diabetic retinopathy. These lesions result from the accumulation of axonal swellings in the nerve fiber layer of the retina.

**Why the Correct Answer is Right**
The pathogenesis of cotton wool spots involves the ischemic injury of retinal nerve fibers, leading to the formation of axonal swellings. These swellings are composed of damaged axonal membranes and organelles, which accumulate in the nerve fiber layer due to impaired axonal transport. The ischemia is often caused by microvascular disease, such as diabetic retinopathy or hypertension, which reduces blood flow to the retina.

**Why Each Wrong Option is Incorrect**
**Option A:** Cotton wool spots are not typically associated with age-related macular degeneration, as this condition primarily affects the macula and does not usually cause retinal ischemia.

**Option B:** While hypertensive retinopathy can cause retinal lesions, cotton wool spots are more specific to diabetic retinopathy and retinal ischemia.

**Option C:** Retinal detachment is a separate condition that can cause visual disturbances, but it does not typically present with cotton wool spots.

**Clinical Pearl / High-Yield Fact**
Cotton wool spots are a type of retinopathy that can be seen in various conditions, including diabetes, hypertension, and retinal vein occlusion. They are often an indicator of underlying retinal ischemia, which can lead to vision loss if left untreated.

**Correct Answer:** D. Diabetic retinopathy.