Diabetes has reached epidemic proportions worldwide. As one of the major complications of diabetes, diabetic retinopathy is a leading cause of blindness that is typically associated with diabetic macular edema. This is caused by the blood vessels of the retina becoming abnormal, causing decreased vision. Normally, blood vessels in the retina do not leak and provide nourishment to the retina and its neural fibers. In diabetic retinopathy, however, the blood vessels leak and cause fluid and blood to enter the retina, particularly the macula. When this becomes swollen and thickened, the macula (center of vision) cannot properly function. This is called macular edema, which causes the central vision to become blurred. This type of leakage in the blood vessels of the retina is called nonproliferative diabetic retinopathy (NPDR) or background diabetic retinopathy (BDR).
Sometimes the blood vessels in diabetes become obstructed, and the part of the retina that depends on those vessels for nutrition is no longer able to function. New blood vessels will then become present to try to provide nourishment to the areas that are no longer able to get the proper nourishment from the blocked vessels. This develops neovascularization, which can cause bleeding and scarring that often leads to severe vision loss and sometimes total blindness. This form of diabetic retinopathy is called proliferative diabetic retinopathy (PDR). Both of these can occur together in the same eye.