Consumers with signs of an early stage of a disease that is the most common cause of blindness in old age can slow down, or in some cases prevent, loss of vision by regularly taking a combination of three antioxidant vitamins and zinc.

American researchers have spent six years looking at the age-related macular degeneration (AMD) and gathering evidence on the impact of multivitamins and zinc. The study followed 3,640 people affected by AMD, between the ages of 55 and 80, who were randomly assigned to take a daily dose of zinc supplements; antioxidants consisting of vitamin C, vitamin E and beta carotene; both zinc and antioxidants; or a placebo.

The researchers found that those with the mildest forms of AMD did not benefit from the supplements; however people with significant vision loss noticed benefits. Most importantly, the study found that after five years, only 20% of those taking zinc and antioxidant supplements developed advanced AMD. This corresponds to 28% of the group who took the placebo.

Ophthalmologist Susan B. Bressler, a leader of the study from the Johns Hopkins Hospital, told the Washington Post: "It's a modest reduction, but given that there's no alternative and that this [treatment] is safe and non-toxic, even a modest reduction is a wonderful thing."

Currently, AMD can only be treated with surgical or quasi-surgical procedures in which the excess blood vessels in the eye are destroyed by laser or light. Bressler commented: "All those interventions do is attempt to limit additional vision loss in people who are already undergoing significant disability.

"We now have an intervention that will decrease the proportion of people who will get to that stage."

Over 8 million elderly people in the US have AMD and could be helped with dietary supplements. The National Eye Institute, the unit of the National Institutes of Health that funded the study, estimates that if those people took supplements for five years, about 250,000 would have noticeably better vision.