Diabetes and vision loss

Seeing the Light

Loss of vision is one of the most troublesome side effects of diabetes – both types 1 and 2. And the risk is enormous: According to the National Eye Institute, more than 40 percent of all diabetics have some stage of diabetic retinopathy – a condition that blocks the capillaries that provide blood to the retina.

The best defense against diabetic retinopathy is early detection. In addition, a new study shows that two vitamin supplements may considerably reduce the risk of this disorder.

Drawing blood

There are no early warning signs for diabetic retinopathy – when the first symptoms are detected, the condition is usually well underway. So in a sense, anyone who is diagnosed with diabetes should consider the diagnosis itself to be an early warning.

Retinopathy begins when elevated levels of insulin and glucose are persistent enough to prompt swelling in the blood vessels of the retina – the light-sensitive tissue at the back of the eye. If swelling persists, blood vessels can become blocked, cutting off the blood supply.

That alone is enough to blur vision, but at this stage the condition may go from bad to worse as the retina tries to correct the problem by developing new blood vessels, which are so thin and fragile that they may leak blood. If this progression isn’t curbed, obstructed vision can evolve into blindness.

Key vitamins to the rescue

A study published in the May issue of the American Journal of Clinical Nutrition examines the effects of dietary and supplemental sources of vitamins C and E on diabetic retinopathy. Researchers in the Department of Ophthalmology and Visual Sciences at the University of Wisconsin (UW), reviewed dietary records of more than 1,300 subjects who participated in a large, multiyear study to assess atherosclerosis risk.

All of the subjects were type 2 diabetics, and 224 were diagnosed with prevalent retinopathy. An analysis of food- frequency and supplement questionnaires showed no association between intake of vitamin C or E from food sources and a reduced risk of retinopathy. But those who reported taking supplements of vitamins C or E for three years or more were found to be significantly less likely to develop retinopathy compared to subjects who didn’t use supplements.

Researchers couldn’t explain why food sources of the vitamins weren’t as effective as supplements. Nevertheless, this study confirms previous animal trials that have shown positive associations between vitamin C and E intake and retinopathy prevention.

Beyond supplementing with vitamins C and E, dietary measures can be taken to help prevent retinopathy. Studies have shown that a deficiency of vitamin B-6 contributes to the condition. Fortunately, B-6 is found in a wide variety of foods including beef, poultry, fish, beans, bananas, spinach, avocados, walnuts and sunflower seeds.

Going digital

The most effective prevention of retinopathy is the control of glucose and insulin levels. Beyond that, a yearly, dilated eye exam is essential. Pregnancy can also raise retinopathy risk, so some doctors recommend several eye exams throughout pregnancy for diabetic women.

In addition to the standard dilated eye exam, a new technology has been developed that requires no dilation. Using a retinal imaging camera, technicians can quickly capture a digital image of the retina, which is then sent over the Internet to retinal specialists for analysis.

Last year, the University of Maryland began an experimental program (funded by a grant from the National Eye Institute) that placed one of these retinal cameras in a Baltimore mall. Two additional cameras were also placed in outlying communities in eastern and western Maryland. I’ll keep tabs on this program and let you know how it progresses. If it’s successful, retinal exams may become as easy as stopping by the Gap to pick up a new pocket-T.

To Your Good Health,

Jenny Thompson
Health Sciences Institute

Sources:
“Relation Between Intake of Vitamins C and E and Risk of Diabetic Retinopathy in the Atherosclerosis Risk in Communities Study” American Journal of Clinical Nutrition, Vol. 79, No. 5, Mary 2004, ncbi.nlm.nih.gov
“Vitamin Supplements Lower Diabetic Retinopathy Risk” D. Dye, Life Extension Foundation, 5/17/04, lef.org
“Diabetic Retinopathy” National Eye Institute, nei.nih.gov
“Telemedicine Program Allows Ophthalmologists to ‘See’ People at Risk for Diabetic Retinopathy and Glaucoma” University of Maryland Medicine, 7/31/03, umm.edu