One of the possible complications of diabetes is a condition called diabetic retinopathy, which causes many of the small vessels that bring blood to the retina to become constricted or damaged. This disorder usually occurs in both eyes. In the early phase of the disease, the remaining blood vessels may leak fluid, causing a permanent distortion of vision. At later stages, new vessels may grow on the retina and leak blood into the eyeball. This will dim or completely obliterate the vision. In both kinds of blood leakage, scar tissue can form on the retina, also causing permanent vision loss.

Because diabetic retinopathy often has no early symptoms, it is vital for all diabetics to have a yearly eye exam by an optometrist. Treatments such as laser surgery are available, but they are more effective the earlier they are used.