However, these ravages are mostly in the past now, and researchers say their decline coincides exactly with the rise of powerful drugs over the past decade.

Some AIDS patients are developing resistance to the drugs that keep them alive, but the rates of CMV-related eye disease remain low. "They're down and staying down. We have all feared a swing back toward higher numbers, but it has not happened," says Dr. Elaine L. Chuang, an associate professor of ophthalmology at the University of Washington School of Medicine.

CMV -- cytomegalovirus -- is present in as many as 85 percent of Americans by the age of 40, according to the U.S. Centers for Disease Control and Prevention. The virus usually settles in before the age of 20 during minor bouts of the flu, Chuang explains.

In almost all cases, the virus lies dormant, although researchers have linked its presence to heart disease and stroke. However, it can awaken in people with severely weakened immune systems and attack various parts of the body, including the gastrointestinal system, the brain and the eyes.

Attacks on the eyes are especially horrific because a disease known as CMV retinitis can destroy the retina, Chuang says. Other CMV-related illnesses, such as a type of pneumonia, can kill.

AIDS patients become especially vulnerable in the last stages of their disease when their immune systems have virtually disintegrated. In the early days of the AIDS epidemic, patients often became infected with CMV retinitis just before they died.

A group of researchers wanted to determine when the eye disease started to wane in AIDS patients, and they turned to studies completed between 1990 and 1996. The results of their investigation, which looked at the records of 681 patients with eye disease and AIDS, appear in the January issue of the Archives of Ophthalmology.

The researchers found the severity of the eye disease cases began to drop in the early 1990s and fell even further in the middle of the decade, says study co-author Janet T. Holbrook, an assistant research professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. The study reports that the severity of eye disease cases dropped by 30 percent thanks to new AIDS drugs that began to appear in the mid-1990s.

The AIDS drugs -- known variously as the "cocktail," "combination therapy" or HAART (highly active anti-retroviral therapy) -- bolster the immune systems of HIV-positive people. For many patients, the drugs have turned AIDS from a fatal disease into a treatable chronic condition.

The early 1990s also brought better powerful drugs to treat CMV retinitis itself, Chuang says. Doctors continue to use those drugs, which remain the standard treatment for the disease.

Now, the number of cases among AIDS patients Chuang sees has dropped so much that it is almost equal to that among another vulnerable group -- people who have had organ transplants. They're at risk because they must take drugs that weaken their immune systems to keep their bodies from rejecting new organs.

However, AIDS patients are far from immune to CMV retinitis, Chuang says. Some don't take their AIDS drugs regularly, especially those who aren't gay men, such as IV drug users. The disease can then take advantage of their weakened immune systems.

The rates of CMV retinitis may remain low, however, as long as people get tested for HIV, the virus that causes AIDS, and seek treatment if needed, she says.

More information

To learn more about CMV, check out the U.S. Centers for Disease Control and Prevention. Eyecenters.com, sponsored by a group of eye doctors, offers this helpful information sheet on CMV retinitis.