Diabetes is a complex disease resulting from the inability of the body to produce insulin, a hormone that takes sugar out of the blood and into cells where it can be used for energy. Without enough insulin, there is too much sugar in your blood. If you have diabetes, you probably already know that one of the common complications of elevated blood sugar is diabetic retinopathy, which is when elevated blood sugar damages the tiny blood vessels in the retina, the light-sensitive tissue that lines the back of the eye. If untreated, diabetic retinopathy can lead to permanent vision loss and blindness.