Madison (WKOW) -- from UW Health: A 25-year study of people with Type 1 diabetes in Wisconsin has some good news: people who controlled their blood-sugar levels over the long term were more likely to reverse certain abnormalities, caused by the disease, in the retina's small blood vessels.
But then there's the bad news: serious eye disease is a very common side effect of diabetes.
Based on the Wisconsin findings, 185,000 to 466,000 Americans with Type 1 diabetes may eventually develop proliferative diabetic retinopathy, a condition that can lead to severe visual impairment.
The study, led by Dr. Ronald Klein, professor of ophthalmology and visual sciences at UW School of Medicine and Public Health, appears in the November edition of Ophthalmology.
Klein and colleagues have been monitoring the health of 996 southern Wisconsin people who were diagnosed with Type 1 (insulin-dependent) diabetes before the age of 30.
The Wisconsin Epidemiologic Study of Diabetic Retinopathy, funded by the National Eye Institute, began in 1979 and followed participants with Type 1 diabetes through 2007.
The research participants had their glycosylated hemoglobin levels (a measure of average blood sugar levels over the previous three months) measured regularly and their eye health checked through photographs of the back of their eyes (the retina) taken with a special camera.
Diabetic retinopathy (signs of damage to the small retinal blood vessels) were detected by grading these photographs at periodic examinations over the 25 years of the study.
Nearly 83 percent of people in the study developed signs of diabetic retinopathy or had their existing diabetic retinopathy worsen.
About 43 percent of study participants went on to develop the most severe stage of diabetic retinopathy, called proliferative diabetic retinopathy, in which abnormal blood vessels grow on the retina.
This growth can cause bleeding and detachment of the retina, leading to severe visual impairment.
Poor blood-sugar control was strongly related to development of proliferative diabetic retinopathy.
Other factors that increased the risk for developing proliferative diabetic retinopathy included being male; being overweight; having higher blood pressure; and having protein in the urine, a sign of diabetic kidney disease.
In about 18 percent of people, the diabetic retinopathy improved.
This improvement was more likely in those with better control of their blood sugar.
There is some other good news in the study.
"Interestingly, we saw less progression to proliferative diabetic retinopathy among people who had a similar duration of Type 1 diabetes but who were diagnosed more recently,'' Klein said. "The biggest reason seems to be an improvement in the management of blood sugar and blood-pressure levels in people with diabetes."
Klein's collaborators include Ronald Gangnon, PhD, of the School of Medicine's Department of Population Health Sciences; and Michael D. Knudtson, MS, Kristine E. Lee, MS; Barbara E.K. Klein, MD, MPH, all of the Department of Ophthalmology and Visual Sciences.