Diabetic retinopathy: fundus camera image of the retina of a human eye showing degenerative exudates (ring of yellow patches) due to diabetes. Diabetic retinopathy is the most common cause of preventable blindness in Western society. Its cause is obscure, although adult non-insulin dependent patients are more susceptible. Early (background) changes involve small arterioles & capillaries, with the formation of microaneurysms (swellings), haemorrhages (leaking vessels) & areas of capillary closure. Progressive loss of vision results from the formation of exudates and the restriction of blood supply.