Diabetic retinopathy is a problem caused by diabetes and which affects the eyes. Sugar has the ability to weaken the blood vessels, including the blood vessels in and around the retina. With diabetic retinopathy, the thin blood vessels in the retina become damaged and they can start to bleed or leak fluids. This can cause bleeding into the vitreous humour. The blood vessels can get closed off after which new, very thin branches develop that can bleed very easily.