Proliferative diabetic retinopathy is the more advanced stage of the disease. New abnormal blood vessels grow over the retina and may grow into the clear vitreous. These new vessels bleed into the vitreous, blocking light from reaching the retina and causing vision to become cloudy. Connective tissue growing along with abnormal blood vessels may contract, pulling the retina off its underlying structures and toward the vitreous (retinal detachment).Proliferative retinopathy affects approximately 5% of all diabetics and becomes more likely with increased duration of diabetes. If left untreated, proliferative retinopathy can lead to blindness.