An estimated 6.5 percent of Americans ages 40 and older have the eye disease age-related macular degeneration (AMD), a lower rate than was reported 15 years ago, according to a new study.

The prevalence of AMD among adults ages 40 and older was 9.4 percent in the years between 1988 and 1994, according to the National Health and Nutrition Examination Survey (NHANES) conducted at the time.

"The decreasing prevalence of AMD may reflect recent change in the frequency of smoking and other exposures such as diet, physical activity and blood pressure associated with AMD, the researchers said in a statement released by University of Wisconsin School of Medicine and Public Health, Madison.

Still, "despite new medical and surgical interventions, age-related macular degeneration (AMD) remains an important cause of loss of vision in the United States," the researchers wrote.

To update the estimate of the conditions prevalence, study researcher Dr. Ronald Klein and his colleagues at the university analyzed data from the 2005 to 2008 NHANES.

Researchers took photos of both eyes of the 7,081 study participants, ages 40 or older, and assessed digital images of the eyes for signs of AMD. They looked for symptoms such as drusen (tiny yellow or white deposits in the retina), pigment changes and atrophy in the retina and surrounding tissue.

The study also showed the estimated prevalence of late (more advanced) AMD was 0.8 percent. Non-Hispanic black people ages 60 and older had a lower prevalence of any type of AMD than non-Hispanic white individuals of the same age.

"These estimates are consistent with a decreasing incidence of AMD reported in another population-based study, and have important public health implications," the authors said.

It remains to be seen, researchers said, whether public health programs designed to increase awareness of how lifestyle choices affect the development of AMD will continue to result in further decline of the prevalence of the condition.

The study was published in the January issue of Archives of Ophthalmology.