Health

The condition, known as diabetic retinopathy, involves damage to the eye's retina and is the leading cause of new cases of legal blindness among U.S. adults between 20 and 74 years old. It also costs the U.S. approximately $500 million every year.

"The number of people with diabetes is increasing in this country," lead researcher Dr. Xinzhi Zhang, of the Centers for Disease Control and Prevention in Atlanta, told Reuters Health.

Yet, he added, estimates of how many Americans suffer from diabetic retinopathy remain more than a decade old. Is this condition on the rise too? Or is screening and treatment keeping it under control?

For some updated answers, Zhang and his colleagues looked to the National Health and Nutrition Examination Survey (NHANES), a large national study conducted between 2005 and 2008. They identified about 1,000 older adults with diabetes who had undergone diagnostic eye imaging.

Of the patients studied, 29 percent were found to have diabetic retinopathy, and 4 percent had developed vision-threatening cases of the disorder.

The rates were about 40 percent and two and a half times higher, respectively, than estimates dating back to an earlier NHANES study from 1988 to 1994.

"But we don't know if the increase is due to an actual rise in prevalence or if it is due to using a more precise method of assessing damage to eyes in the most recent study," noted Zhang, pointing out that the new study included two digital images of each eye compared to the previous study's single image of one eye.

The researchers found that men had a significantly higher risk of developing diabetic retinopathy compared to women. Other risk factors included a longer duration with diabetes, use of insulin, high systolic blood pressure (the top number in the reading) and high levels of a protein called hemoglobin A1c used to measure blood sugar.

Mexican Americans and non-Hispanic blacks also had significantly higher rates of the condition compared to non-Hispanic whites, report the researchers in the Journal of the American Medical Association.

As the U.S. population ages and the proportion of racial minorities grows, it is important for the health care system to be prepared for the increasing demand, said Zhang. "With early detection and timely treatment, people have a good chance of preventing or reducing vision loss."

As of 2007, 17.4 million Americans had diagnosed diabetes, with the highest percentage of cases found among people over 65, according to the U.S. Centers for Disease Control and Prevention.

Zhang added that it is also crucial for people with diabetes to control their blood sugar, cholesterol and blood pressure to help prevent complications such as diabetic retinopathy in the first place, and for those who don't already have diabetes, to stave off the condition by losing weight and exercising.