Microaneurysms are the earliest clinical sign of diabetic retinopathy and occur secondary to capillary wall outpouching due to pericyte loss that leak plasma constituents into the retina. They may be clinically indistinguishable from small dot and blot hemorrhages.

Dot and blot hemorrhages

Dot and blot hemorrhages occur as microaneurysms rupture in the deeper layers of the retina, such as the inner nuclear and outer plexiform layers. These appear similar to microaneurysms if they are small.

Flame-shaped hemorrhages

Flame-shaped hemorrhages are splinter hemorrhages that occur in the more superficial nerve fiber layer.

Retinal edema and hard exudates

Retinal edema and hard exudates are caused by the breakdown of the blood-retina barrier, allowing leakage of serum proteins, lipids, and protein from the vessels.

Cotton-wool spots

Cotton-wool spots occur secondary to ischemia from retinal arteriole obstruction. It is thought to represent nerve fiber layer infarct and pre-capillary arteriolar occlusion.

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