The pictures below show patients with moderate non-proliferative diabetic retinopathy. There are various types of hemorrhages. Cotton wool spots are areas of focal oxygen deprivation. microaneurysms are outpouchings of capillaries that can leak. Exudates are the leakage of blood serum from capillaries.
If the oxygen deprivation is severe enough, new blood vessels (neovascularization) will begin to form in the attempt to reperfuse the retinal tissue. However, these new blood vessels are very leaky and certain contents from the blood destroy the retina, thereby causing severe vision loss. When new blood vessels grow, retina specialists often will perform pan-retinal photocoagulation, or PRP. PRP selectively destroys much of the peripheral retina, thereby decreasing the oxygen deman in the eye. This decreased oxygen demand allows the most important central part of the eye to receive enough oxygen to prevent neovascularization. The photo below shows the laser scars that result in the peripheral retina from PRP.