ABSTRACT
Diabetic retinopathy is the most common chronic complication of diabetes mellitus and is the most common cause of blindness in middle-aged subjects in the United States and the United Kingdom. The prevalence of diabetic retinopathy is almost 100% in patients with type 1 diabetes and over 60% in patients with type 2 diabetes in whom the disease has been present for more than 20 years. Diabetic retinopathy is the result of several pathological processes that include loss of capillary pericytes, damage to capillary wall resulting in increased permeability and weakness of capillary wall, microvascular occlusion leading to retinal ischemia, and proliferation of new blood vessels. Microaneurysms, hypercellular outpouchings from the capillary wall, are the earliest signs of diabetic retinopathy. The hallmark of proliferative retinopathy is retinal and preretinal neovascularization that occurs in response to the increased retinal ischemia. Presumably, the nutrient-starved retina sends out a chemical message to stimulate the growth of new blood vessels.
