Diabetics who are able to keep their blood-sugar levels well regulated are much less likely to go blind than those whose levels are poorly controlled, according to research published Friday.

The findings were reported in Journal of the American Medical Association.Thousands of diabetics lose their sight each year because of a diabetes-linked condition called retinopathy, in which tiny blood vessels at the back of the eye break and bleed, usually painlessly over a period of years.

Researchers at the University of Wisconsin used blood sugar-levels to divide subjects into four categories and found that those in the highest-level category developed signs of retinopathy almost twice as often as subjects in the lowest category.

For example, the four-year risk of developing advancing retinopathy among people with an 11 percent reading for glycosylated hemoglobin, a blood-sugar test, was estimated to be roughly double that of people with a reading of 9 percent, the researchers said.