Too much glucose, blood sugar, can cause problems all over your body, eyes included. In particular, there are four parts of the eye that are vulnerable to high blood sugar: the retina, the lens, the vitreous gel, and the optic nerve. The retina stretches over the back of the eye, kind of like a screen for the light that enters your eye. Images projected onto your retina are converted into signals your brain can interpret and transmitted through your optic nerve. Diabetics may develop a condition called diabetic retinopathy in which the blood vessels in your retina become damaged. The blood vessels could begin to leak, or new blood vessels can grow and obscure the retina. Either way, dark patches will begin to obscure vision, and even lead to blindness.
Non-proliferative (background) – The longer you have diabetes, the greater the risk of small blood vessels at the back of the eye being damaged by high blood glucose and high blood pressure. This can result in leakage and often progresses to blockage of the vessels that supply the retina with nutrients. This stage is called non-proliferative or background retinopathy and there may be no noticeable change in your vision.
Proliferative – Non-proliferative diabetic retinopathy can progress and the retina may grow new blood vessels. This advanced stage is called proliferative retinopathy. The new blood vessels are weaker and can bleed onto the retina or the vitreous, the jelly-like centre inside your eye. Vision can be affected, sometimes seriously and suddenly.