Diabetes damages the blood vessels in the retina causing the vessels to leak fluid and blood, and in severe cases to close off completely. This results in swelling of the retina, loss of blood flow to the retina and blurred vision. In some cases abnormal blood vessels may grow on the surface of the retina or on the iris. When these changes are seen the patient has diabetic retinopathy. There are two types of diabetic retinopathy, nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR).
In nonproliferative diabetic retinopathy the damaged retinal vessels leak fluid, small amounts of blood, and sometimes fatty material. If fluid leakage occurs in the central part of the retina, the macula, vision will be blurred. Vision loss can also occur if the tiny retinal vessels that feed the macula close off. In proliferative diabetic retinopathy, PDR, there is extensive damage to retinal vessels where many of the vessels close off depriving retinal tissue of oxygen and nutrients. The eye responds to this insult by producing abnormal blood vessels in an attempt to nourish the tissue. These abnormal blood vessels are fragile and easily bleed resulting in significant loss of vision. Also with the growth of abnormal blood vessels, scar tissue forms resulting in distortion of the retina and sometimes retinal detachment.
Treatment of both types require laser treatment and/or injections of medications into the eye to reduce the swelling of the retina or to stop the growth of new vessels. Usually multiple treatments are needed. If significant bleeding occurs in the eye or if there is significant scar tissue causing detachment of the retina surgery may be required.
It is important for diabetic patients to have regular eye exams and to keep their blood sugar under control. Equally important, keeping blood pressure and blood lipid levels in the normal range will help improve retinopathy. Patients with diabetes should be seen at least once a year. If retinopathy is present more frequent visits may be necessary.