The objective of this research study is to evaluate the relationship between sickle cell trait and the progression of diabetic retinopathy. People with diabetes have high blood sugar that damages small blood vessels. Damage to the blood vessels that supply the retina in the back of the eye is called diabetic retinopathy. Diabetic retinopathy is worse in African-Americans with diabetes, with earlier and more severe disease progression and common complications including vitreous hemorrhage - where these blood vessels in the eye leak - and retinal detachment - the separation of the nerves of the retina from the back of the eye which may lead to blindness. One explanation for this increased severity of diabetes in African-Americans is the presence of sickle cell disease, or even just sickle trait, which causes damage to red blood cells and blood vessels under conditions of stress; like low oxygen levels, or hyperglycemic acidosis.