Diabetic retinopathy is a condition which affects some diabetics after a number of years, depending on how well their insulin levels are controlled.

In 'non-proliferative' retinopathy the blood vessels in the retina dilate, altering the blood flow in the retina. The condition usually causes no symptoms and isn't sight-threatening, but it needs to be monitored carefully because it might signal future damage to the back of the eye.

In 'proliferative' retinopathy, which can develop from the non-proliferative stage, new blood vessels form in the eye. These vessels are extremely weak and also in the wrong place; as a result, the vessels can break and leak blood. This causes both scar tissue to develop and the fluid in the eye to become cloudy. Occasionally, retinal detachment can occur too.