Many people who have Type 1 or Type 2 diabetes develop retinopathy, a serious disorder that damages the eye's retina, the area of the back of the eye where images are focused and relayed to the brain's visual cortex. Ophthalmologists (Eye M.D.s) monitor their diabetic patients for signs of retinopathy and use lifestyle recommendations, medications, and surgical approaches as appropriate to reduce the risk that diabetic retinopathy (DR) will progress to the proliferative stage (PDR), in which abnormal blood vessel growth leads to visual impairment.
In recent years the diagnosis, prevention and treatment of DR and PDR have improved markedly.
The Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) is a large, long-term study that confirmed and expanded on results of other significant DR studies such as the Diabetes Control and Complications Trial. Ronald Klein, MD, and colleagues evaluated factors associated with the progression or regression of retinopathy over a 25 year period in people who had been diagnosed with Type 1 diabetes before the age of 30 years. The key finding was that glycemic control---assessed via blood levels of glycosylated hemoglobin A1, a reliable measure of average blood sugar---at the time of the baseline exam and throughout the study was strongly related to whether a patient's DR worsened or improved.
This confirmed findings of a number of earlier large studies. Better glycemic control was associated with significant reduction in DR progression and increased improvement in DR independent of how long the patient had had Type 1 diabetes and the level of DR at the baseline exam. Other risk factors found by the WESDR to be associated with progression to PDR included male gender, higher blood pressure level, presence of protein in urine (a manifestation of diabetic kidney disease) and a greater body mass index as measured at baseline.
WESDR participants were 955 insulin-taking Type 1 diabetics who received baseline exams between 1980 and 1982 and were either evaluated again four years later or died before the four-year follow up. Additional follow up exams were done at 10, 14 and 25 years post-baseline, and 520 of the original participants completed the 25-year follow-up.
Based on WESDR findings, the researchers estimate that over a 25-year period, 185,000 to 466,000 Americans with Type 1 diabetes will develop PDR. Dr. Klein adds the caution that these numbers may be an overestimation, because PDR incidence has declined in people diagnosed with Type 1 diabetes in recent years, possibly due to proactive and improved treatment of glycemia and blood pressure.
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