There are two types of diabetic retinopathy:
Background retinopathy
This is the most common form of diabetic retinopathy. It is caused by different types of problems with existing blood vessels within the eye. The problems involve bleeding from blood vessels and leakage of fats and fluids into the tissue of the eye. If these problems occur in one particular part of the eye (the macula), reduced vision will result. Normally, though, this form has no effect on vision and needs no treatment. Sometimes, though, it can lead to the more serious form.
Proliferative retinopathy
This is a more serious condition and starts out as background retinopathy. It is caused by the growth of very fine, delicate blood vessels which tend to bleed very easily. The bleeding itself can cause problems with vision, as can the scar tissue, which may form at the point that bleeding occurs.