Too much sugar in the blood can lead to the blockage of tiny blood vessels in the retina, cutting off its blood supply, meaning new blood vessels do not develop properly.
There are two types of diabetic retinopathy:
Early diabetic retinopathy: This is the most common form, called non-proliferative diabetic retinopathy (NPDR), and many people with diabetes have this condition. With NPDR, tiny blood vessels leak, making the retina swell. When the macula swells, it is called macular edema. This is the most common reason why people with diabetes lose their vision.
Advanced diabetic retinopathy: Diabetic retinopathy can progress to this more severe type, known as proliferative diabetic retinopathy. This is where damaged blood vessels close off, causing the growth of new, abnormal blood vessels in the retina