Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in North American adults. It occures blood vessels may swell and leak fluid. The National Eye Institute website which can provide a detailed explaination of diabetic retinopathy.
The best way to monitor for signs of diabetic retinopathy is to take retinal photos. Below are some examples of diagrams of a retina and photos of someone with diabetic retinopathy. (click on photos to enlarge)
Michael Nelson, OD