A simple regimen of eyedrops could delay or prevent the onset of one of the leading causes of blindness in the U.S. According to a report published in the June issue of the Archives of Ophthalmology, drops that reduce eye pressure slow the development of glaucoma.

The most common form of the disease, so-called primary open-angle glaucoma, is known to affect some 2.2 million Americans ages 40 and over. But it may afflict as many as two million more who haven't been diagnosed. "Glaucoma is often referred to as the 'sneak thief of sight' because it often occurs with no pain or symptoms," says Ronald L. Gross of the Baylor College of Medicine, a co-author of the new study. "Many times patients don't notice a difference in peripheral vision until the problem has progressed. Therefore, it is essential to visit an ophthalmologist to detect the condition early."

Glaucoma is associated with a number of risk factors, high eye pressure being one of the strongest. As a result, doctors have prescribed medications to ease that condition as a way of staving off the disease. Whether such treatments actually have a long-term benefit, however, was unclear. In the new study, which spanned a five-year period, investigators followed 1,636 people between ages 40 and 80 who had elevated eye pressure but not glaucoma. Half were randomly selected to use commercially available, pressure-lowering drops each day. Strikingly, the drops--which reduced eye pressure by around 20 percent--cut the rate of glaucoma occurrence in half: whereas 9.5 percent of the study participants who did not receive drops developed glaucoma, only 4.4 percent of the medicated subjects did.

"I think it is very significant that reducing pressure in the eye by only 20 percent reduced risk by as much as it did," remarks team member Michael A. Kass of Washington University. "A modest drop in pressure makes a big difference." Still, the researchers caution that not all individuals with elevated eye pressure should automatically turn to medication. "Before simply putting a patient on drops, doctors need to consider the patient's general health status, their individual risk factors and their life expectancy, Kass says. "It's important to remember that even in the study group that did not receive treatment, 90 percent of the people did not develop glaucoma." Because some eyedrops can cause side effects and daily treatment can be inconvenient and costly, he notes, certain patients may be better off choosing close observation over medication.