By David Mallory M.D.

    Twelve million Americans have diabetes. For everyone diagnosed as diabetic, there is one undiagnosed who does not know that he or she has this condition.

    Although the incidence of cataracts is five times as high and glaucoma is twice as high in diabetics, it is the effect of diabetes on the retina that causes the most damage. The retina lines the inside of the eye and is the actual "seeing" part of the eye.

    Diabetic retinopathy is the leading cause of blindness in adults younger than age 65.
Diabetes attacks the tiniest blood vessels in the retina, called capillaries, causing them to leak fluid (edema) and become brittle or sclerotic and close up. There are two treatable and possibly preventable reasons why eyes can lose vision in diabetes.

    The first is from swelling in the central vision area of the retina, called the macula. The second is from bleeding into the eye from fragile new blood vessels caused by not enough oxygen getting to the retina.

    Two large national studies have shown that laser photocoagulation can dramatically decrease the incidence of visual loss in diabetes. The first was completed in 1979 and showed a 50 to 65 percent decrease in severe visual loss in high risk diabetic patients who had new blood vessel growth into the eye, but early diagnosis and treatment were found to be critical.

    Another study also emphasized the importance of early treatment. People with diabetes may develop swelling in the macula, the part of the retina that specializes in seeing small things. They may have edema even if their vision is 20/20 and they have no visual complaints. Treatment of the swelling with a laser over a three-year period cut loss of vision in half, from 24 to 12 percent. Very few patients, however, were able to recover vision already lost.

    The possibility of retinal problems from diabetes increases with how long the person has been diabetic and how well their blood sugar has been controlled. High blood pressure and perhaps smoking have been shown to make the retinopathy worse. Some studies have shown Mexican Americans to be at higher risk.

    It is important that people with diabetes know that they may have retinal problems that are sight threatening, even though they seem to have no visual problems. When they do occur, it may be too late to restore full vision or to stop further deterioration with laser photocoagulation. Early detection depends on regular, thorough eye examinations.

David Mallory, M.D. is a cataract, intraocular lens and laser surgery specialist in practice at the Southwest Eye Clinic.

Copyright 2013 David Mallory, M.D., Inc. All rights reserved.
For more information, please email Dr. Mallory