Bloomberg — More than one in four diabetics ages 40 or older has eye damage from the disease, signalling a greater need for access to care, researchers from the US Centers for Disease Control and Prevention found.

Some 28.5 percent of diabetics in the nation, or 4.2 million people, suffer from diabetic retinopathy, a progressive disease that is the leading cause of blindness in adults, the scientists said in the Journal of the American Medical Association. About 4.4 percent, or 655,000, have the most severe stage of the disease that left untreated can lead to vision loss, the authors said.

The study is the first in almost a decade to estimate the prevalence of the eye malady nationwide, said the author, Xinzhi Zhang, an epidemiologist with the Atlanta-based CDC. As the U.S. population ages and there's growth in groups, such as Mexican Americans and blacks, that are less likely to be screened for disease, diabetic retinopathy may become more common, he said.

"The health-care system, it needs to be prepared for such increasing demand," Zhang said today in a telephone interview. "We need to increase awareness and let more physicians, providers and patients know the importance of getting eye exams."

About 23.5 million Americans, or about 11 percent of people ages 20 or older, have diabetes, according to the American Diabetes Association, based in Alexandria, Virginia. About 11.8 percent of non-Hispanic blacks and 10.4 percent of Hispanics have the illness.

Diabetic retinopathy occurs when there are changes to the blood vessels of the retina, the membrane at the back of the eye. The longer people have diabetes and the less controlled their blood sugar is, the more likely they are to develop the eye disease, according to the Mayo Clinic in Rochester, Minnesota.