**Core Concept**
Snow banking is a phenomenon observed in certain retinal conditions where there is a deposition of hard exudates in the perifoveal area, resembling a snowbank. This condition is often associated with diabetic retinopathy. The hard exudates are composed of lipid deposits that accumulate in the retinal pigment epithelium due to the breakdown of the blood-retinal barrier.

**Why the Correct Answer is Right**
In diabetic retinopathy, the breakdown of the blood-retinal barrier leads to the leakage of lipids, including triglycerides and cholesterol, from the retinal capillaries into the surrounding retina. This leakage results in the formation of hard exudates, which can accumulate in the perifoveal area, giving the appearance of snow banking. The retinal pigment epithelium plays a crucial role in the pathogenesis of snow banking by allowing the lipid deposits to accumulate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because snow banking can be a feature of other conditions, such as hypertensive retinopathy, where the deposition of hard exudates is not limited to the perifoveal area.
**Option B:** This option is incorrect because snow banking is a distinct clinical feature that is not typically associated with retinal vein occlusion, which is characterized by retinal hemorrhages and cotton wool spots.
**Option C:** This option is incorrect because snow banking is not a feature of retinal detachment, which is characterized by the separation of the retina from the underlying retinal pigment epithelium.

**Clinical Pearl / High-Yield Fact**
It is essential to distinguish between hard exudates and cotton wool spots, as they have different implications for patient management. Hard exudates are often associated with diabetic retinopathy and may indicate the presence of macular edema, whereas cotton wool spots are more commonly seen in hypertensive retinopathy and may indicate retinal ischemia.

**Correct Answer:** D.