Can someone with just a slightly high blood sugar level (not diabetes) develop diabetic retinopathy?

Yes: High blood sugar over a period of years will cause diabetic retinopathy. The line between high blood sugar and diabetes can be fuzzy. Anytime sometime is diagnosed as prediabetic, it is important to get yearly dilated eye exams from an ophthalmologist. Often diabetic eye disease can be assymptomatic in its early stages but most easily treated then.

Maybe?: The sugar level varies throughout the day, so what is slightly high? If you're asking can borderline diabetics develop dr, certainly, but it may take a lot longer than for someone who does have diabetes.

Diabetic retinopathy: The course of diabetic retinopathy (dr) varies from person to person and is dependent on how long they have their diabetes and how well controlled it is. How do you know you are not diabetic? Is your hb a 1c normal, or elevated? Dr is dependent on two things, glucose and hbp control. Looking at the figure, you can see that BP control reduces dr better than glucose control. Speak to your physician.