Question: what are the four stages of diabetic retinopathy?
Answer: Mild Nonproliferative Retinopathy. At this stage, microaneurysms occur. ... 
Moderate Nonproliferative Retinopathy. This stage is when blood vessels that nourish the retina are blocked.
Severe Nonproliferative Retinopathy. ... 
Proliferative Retinopathy.