More Americans facing blindness than ever. (Advertising Supplement).

More Americans than ever are facing the threat of blindness from age-related eye disease, a new report says. Over one million Americans aged 40 and over are currently blind and an additional 2.4 million are visually impaired. These numbers are expected to double over the next 30 years as the Baby Boomer generation ages.

The Vision Problems in the U.S. report on the prevalence of sight-threatening eye disease in Americans was released today by the National Eye Institute, in partnership with Prevent Blindness America.

"Blindness and visual impairment from most eye diseases and disorders can be reduced with early detection and treatment," U.S. Secretary of Health and Human Services Tommy G. Thompson. "That's why eye health education programs that encourage those at high risk for eye disease to have regular dilated eye exams are essential in preventing vision loss. Healthy vision is a shared responsibility among the government, health care providers, community leaders, and the public."

The director of the National Eye Institute, Paul A. Sieving, M.D., Ph.D., called for an increase in public attention to eye disease. "About one in eight Americans is 65 or older," Dr. Sieving said. "When you add declining mortality rates and population shifts, such as the 'baby boomers,' the number of older people will grow dramatically in the years ahead. Blindness and vision impairment represent not only a significant burden to those affected by sight loss, but also to the national economy as well."

The new report addresses the leading causes of vision impairment and blindness in the U.S., including:

Diabetic retinopathy, believed to be a leading cause of blindness in the industrialized world in people between the ages of 25 and 74. Diabetic retinopathy affects more than 5.3 million Americans age 18 and older.

Age-related macular degeneration (AMD), the most common cause of blindness and vision impairment in Americans aged 60 and older. More than 1.6 million Americans over age 60 have advanced AMD.

Cataract, the leading cause of blindness in the world. Cataract affects nearly 20.5 million Americans age 65 and older.

Glaucoma, a chronic disease that often requires life-long treatment to control. About 2.2 million Americans have been diagnosed with glaucoma, and another two million do not know they have it.

The Vision Problems in the U.S. study was the result of a 2001 consensus meeting, convened by the National Eye Institute and involving many of the world's leading ophthalmic epidemiologists. Data were obtained from a systematic review of the major epidemiological studies with the cooperation of their authors. National data are broken down into state-by-state statistics.

"These are the most comprehensive data available on the prevalence of eye disease in America," said David S. Friedman, M.D., M.P.H., principal investigator of the study, and Assistant Professor of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University. "We hope this information will serve as a guide to our communities and our nation's leaders. We must comprehend the scope of eye problems in our country so that adequate resources can be devoted to research, treatment, and prevention."

A copy of the full report is available in downloadable format at www.preventblindness.org and www.nei.nih.gov/eyedata

Major eye diseases

The leading causes of vision impairment and blindness in the U.S. are diabetic retinopathy, age-related macular degeneration, cataract, and glaucoma.

Diabetic retinopathy is a common complication of diabetes. Retinal blood vessels can break down, leak, or become blocked, affecting and impairing vision over time. Nearly half of all people with diabetes will develop some degree of diabetic retinopathy during their lifetime, and risk increases with age and duration of diabetes. People with diabetes are encouraged to seek annual dilated eye exams. Currently, laser surgery and a procedure called a vitrectomy are highly effective in treating diabetic retinopathy. Research into pharmaceutical treatment options is continuing.

Age-related macular degeneration is a condition that primarily affects the part of the retina responsible for sharp central vision. There are two forms of AMD -- dry AMD and wet AMD. Because AMD often damages central vision, it is the most common cause of legal blindness and vision impairment in older Americans (AMD rarely affects those under the age of 60). While there is no generally accepted treatment for dry AMD, laser therapies to destroy leaking blood vessels can help reduce the risk of advancing vision loss in many cases of wet AMD. Research sponsored by the National Eye Institute has recently shown that a combination of zinc, vitamins C and E, and betacarotene may also reduce the risk of advanced AMD by 25 percent.

Cataract is a clouding of the eye's naturally clear lens. Most cataracts appear with advancing age. Scientists are unsure what causes cataract. The most important factor is increasing age, but there are additional factors, including smoking, diabetes, and excessive exposure to sunlight. Cataract is the leading cause of blindness in the world, and affects nearly 20.5 million Americans age 40 and older. By age 80, more than half of all Americans develop cataract. Cataract is sometimes considered a conquered disease because surgical treatment that can eliminate vision loss due to the disease is widely available. However, cataract still accounts for a significant amount of vision impairment in the U.S., particularly among people age 65 and over who may have difficulty accessing appropriate eye care.

Glaucoma is a disease that causes gradual damage to the optic nerve, that carries visual information from the eye to the brain. The loss of vision is not experienced until a significant amount of nerve damage has occurred. For this reason, as many as half of all people with glaucoma are unaware of their disease. About 2.2 million Americans age 40 and older have been diagnosed with glaucoma, and another two million do not know they have it Most cases of glaucoma can be controlled and vision loss slowed or halted by timely diagnosis and treatment. However, any vision lost to glaucoma cannot be restored.

Michael Coogan is with the National Eye Institute (NEI), part of the National Institutes of Health (NIH).

Daniel Garrett is with Prevent Blindness America, the nation's leading volunteer eye health and safety organization.