Long-standing diabetes can damage the blood vessels in the retina. This is called diabetic retinopathy. Not all persons who have diabetes develop impaired vision. Severity of the retinopathy and the accompanying loss of vision depend on several factors including the kind of diabetes you have, age of onset, length of time you have had diabetes, and how well your blood sugar levels have been controlled.
If you have diabetes, you should have eye examinations, at intervals prescribed by your doctor, to determine whether diabetic retinopathy is present. Treatment of retinopathy with lasers at the appropriate time may delay or stop progression. If any retinopathy is found, then regular exams should be performed by an ophthalmologist to evaluate the degree of damage and advise treatment.