Patients with diabetes mellitus experience an inability to use and store sugar. Blood sugar levels in these patients can be so elevated as to damage the blood vessels of the eyes. Diabetic retinopathy is one of the most common complications associated with diabetes, and is the leading cause of blindness among working-age Americans.
Damaged blood vessels in the retina leak fluid or bleed. This causes the retina to swell and form deposits called exudates. In the early form of diabetic retinopathy, called nonproliferative or background retinopathy, patients may not notice any change in vision. However, in proliferative retinopathy, new, fragile blood vessels grow on the surface of the retina. This neovascularization can lead to serious vision problems when new vessels break and bleed into the clear, jelly-like substance that fills the center of the eye, called the vitreous. Clouding of the vitreous by blood prevents light from passing through the eye to the retina. This can blur or distort vision. The new blood vessels can also cause scar tissue to develop, which can pull the retina away from the back of the eye. This is known as retinal detachment, and can lead to blindness if untreated.