Definition:

Diabetic retinopathy (DR), one of the most common vascular complication of diabetes, is the leading cause of visual deficits and blindness around the world. The development of DR is divided into two stages: in the early stages, also called as nonproliferative stage, it is asymptomatic because the signs are not visible to the eye. however, some defects including microaneurysms, intraretinal hemorrhaging, narrowing or blocked retinal blood vessels can be seen by detection; in the second stage, known as proliferative diabetic retinopathy, where neovascularization appears at the back of the eye and extend into the vitreous of the eye, and these new blood vessels are fragile. If they leak blood, the bleeding causes shrinkage of the retina, leading to retinal detachment, and ultimately to blindness. It has been reported that vascular endothelial growth factor A, angiotensin-converting enzyme, paraoxonase, erythropoietin are associated with DR development and progression.