What causes hard exudates on the retina?

Hard exudates on the retina are primarily caused by the leakage of lipoproteins out of blood vessels. These exudates are characterized by their yellow-white appearance with well-defined edges, and they result from the accumulation of lipids that seep from damaged or permeable retinal blood vessels, typically seen in conditions like diabetic retinopathy and hypertension.

The process involves the breakdown of the blood-retinal barrier, leading to the escape of plasma components, including lipoproteins, which then deposit on the retinal surface. This is a key pathological finding as it indicates underlying vascular issues in the retina.

In contrast, blood vessel rupture is typically characterized by the presence of hemorrhages rather than hard exudates. Inflammatory changes in surrounding tissue might lead to other types of retinal findings but are not directly responsible for hard exudates. Infection in the retina can cause numerous changes, including exudates, but these are usually different in appearance and nature, often associated with more severe conditions or symptoms. Thus, the leakage of lipoproteins is the specific cause of hard exudates on the retina.