New research targets diabetics' vision problems

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New research targets diabetics' vision problems
Early recognition of diabetic retinopathy can lead to more effective treatment.

Oct. 9, 2006
By Susan J. Landers
American Medical News

Washington -- If there weren't already enough good reasons for tight glucose control among diabetic patients, lowering the risk of blindness provides another.

Diabetic retinopathy, a long-recognized complication of both type 1 and 2 diabetes, is a leading cause of blindness. It results from damage incurred by blood vessels in the retina and is the target of new research conducted by the Diabetic Retinopathy Clinical Research Network, a 4-year-old collaborative venture designed to bring promising treatments to patients as quickly as possible.

Concern is growing that this diabetes complication is likely to be seen more frequently as the collective expansion in the nation's waistline is expected to lead to an increase in the number of people with diabetes, said a network researcher who spoke at a Sept. 19 Capitol Hill briefing.

Thomas W. Gardner, MD, a professor of ophthalmology, cellular and molecular physiology at Milton S. Hershey Medical Center in Pennsylvania, described diabetic retinopathy as trying to look at something with a thumb over your eye -- a problem similar to that faced by people with macular degeneration.

The briefing was sponsored by the Alliance for Eye and Vision Research with the American Diabetes Assn. and the Juvenile Diabetes Research Foundation International.

Research already has brought about many treatment gains for this eye disorder, Dr. Gardner said. Lasers have been employed effectively to prevent additional vision loss, as have vitrectomies to remove the leaked blood that often blocks vision.

As a result, blindness is much less likely today than it was in the past. Thirty years ago, half of the nearly one million patients who developed severe diabetic retinopathy went blind within five years of diagnosis. Today, that figure has declined by 90%, according to National Institutes of Health figures.
Stepped-up screening needed

But continued improvement is still possible, and early recognition of both diabetes and its complications is key, experts say. Even people who are pre-diabetic and whose blood glucose levels are higher than normal but not high enough to be diagnosed as diabetic are more likely to be threatened by diabetic retinopathy than are those whose glucose levels are normal, according to recent research.

Nearly 8% of more than 3,000 pre-diabetic participants in the NIH's Diabetes Prevention Program were found to already have the complication. That finding reinforced the need for screening, said researchers from the National Eye Institute, who released their findings in 2005.

Screening among African American patients with diabetes is also deficient, according to a study in the September Archives of Ophthalmology. Researchers from the University of Medicine and Dentistry at the New Jersey Medical School in Newark and Kean University in Union, N.J., found that diabetic retinopathy among their study population of 725 African-Americans with type 1 diabetes moved progressively to a serious stage during the six-year-study. They also noted that the group had poor blood glucose control as well as high blood pressure.

A focus of the diabetic retinopathy research network is to include community-based diabetes programs as well as academic centers. It collaborates with practicing physicians to bring cutting-edge treatments to patients in all settings, Dr. Gardner said.

So far, the research network, which is funded by the eye institute, includes 99 sites in 43 states and 545 investigators, he said. Eight studies with 1,700 patient-participants have been completed, including several on improving laser treatment and another on the use of bevacizumab, or Avastin, for use in diabetic retinopathy. The drug is approved for treating colon cancer.

Several new findings also have resulted from network-run research that may have an impact on treatment, Dr. Gardner said. Among them: Diabetes affects the entire retina, not just blood vessels; and lack of insulin action -- not just high glucose -- also takes its toll on the retina.

ADDITIONAL INFORMATION:
Recent discoveries on diabetic retinopathy

* NIH researchers found that a protein called vascular endothelial growth factor spurs the development of the abnormal blood vessels that invade the retina to cause blindness. Additional evidence suggests that the gene that encodes the protein can be regulated therapeutically to prevent blood vessels from growing.
* Numerous clinical trials are testing pharmacologic agents to control the protein's action.
* A high resolution imaging technology called optical coherence tomography has been developed to allow physicians to definitively diagnose diabetic retinopathy in its earliest stage.
* Early detection and regular follow-up to monitor a patient's disease are essential.

Source: National Institutes of Health

Copyright 2006 American Medical Association. All rights reserved.