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November 7, 2001


How Diabetes Can Adversely Affect Your Eyes

November 1-30 is Diabetic Eye Disease Awareness Month. Many are unaware that diabetes can lead to vision loss when untreated. Ophthalmologists at the Emory Eye Center routinely treat patients who have the particular complications of diabetes that affect their vision.

Diabetic retinopathy is a complication of diabetes, which can weaken the retina and block, distort or blur vision. While no one knows why diabetes sometimes causes abnormal blood vessels to form in the back of the eye, current research is providing some answers. With diabetic retinopathy these new vessels can leak fluid into the retina or vitreous humor (the jelly that fills the eye) and contract, distort or detach the retina.

Retinopathy is strongly linked to duration, so that people who have had diabetes for 15 years or more are at strong risk of developing this sight-stealing disease. It affects some 8,000 diabetics each year in this country and is the leading cause of blindness in adults age 20 to 74, according to the American Academy of Ophthalmology.

The early stage of diabetic retinopathy is nonproliferative diabetic retinopathy (NPDR), which occurs when tiny blood vessels within the retina leak blood or fluid. The leaking fluid causes the retina to swell or to form deposits called exudates. Many with diabetes have mild NPDR, which does not typically affect their vision. When vision is affected, it is the result of macular edema (swelling of the macula) and/or macular ischemia (when small blood vessels close). Proliferative diabetic retinopathy (PDR) is present when abnormal, new vessels (neovascularization) begin growing on the surface of the retina or optic nerve. Adequate blood supply is prevented, causing the retina to respond by growing these new vessels. Unfortunately, the new vessels do not resupply the retina with normal blood flow, and these new vessels are often accompanied by scar tissue that may cause wrinkling or detachment of the retina.

PDR causes more severe vision loss when the new vessels bleed into the vitreous, the clear, jelly-like substance that fills the eye. A very large hemorrhage might block all vision. Smaller ones cause dark floaters in one's vision. With time, this new blood in the vitreous may clear.

A medical eye examination is the only way to find these changes inside the eye. An ophthalmologist can often diagnose and treat serious retinopathy before the patient is aware of any problems.

"Our recent studies suggest that rigid control of diabetes dramatically reduces secondary complications, including eye, kidney, heart and vascular problems," says Thomas Aaberg, Sr., a leading retina surgeon and director of the Emory Eye Center. "Rigid control means using an insulin pump or injecting insulin more than one time a day. Once diabetics have proliferative retinopathy, tight control will not cause reversal of the problem, but the disorder is preventable and very treatable with continuous medical treatment and a yearly exam by an ophthalmologist."

If vision is in jeopardy from nonproliferative retinopathy, Dr. Aaberg may recommend laser photocoagulation surgery, which seals the leaking vessels without an incision. Emory participated in two National Institutes of Health-sponsored studies that showed the procedure can prevent vision loss by reducing abnormal blood vessel growth and reducing the blood vessel leakage (edema).

If the vitreous becomes clouded with blood, Dr. Aaberg may rarely recommend cryotherapy, an outpatient procedure during which a freezing probe is applied to shrink the abnormal blood vessels. In the most severe cases, he may suggest a vitrectomy to remove the vitreous humor and replace it with a clear solution.

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