Age related macular degeneration (AMD) is the main cause of sight loss as people age.

AMD is a condition which causes light sensitive cells at the back of the eye to stop working, resulting in severe vision loss; it affects the central vision, needed for driving and for many other activities.

Now a new study by researchers in the U.S. has found that regular exercise could reduce the risk of the age-related eye disease.

Researchers from the University of Wisconsin tracked almost 4,000 men and women over a 15 year period by conducting regular eye tests and recording levels of exercise.

They found those with an active lifestyle were 70% less likely to develop the degenerative eye disease than those with a sedentary lifestyle.

The study of 3,874 men and women in Beaver Dam, Wisconsin began in 1988 and they were assessed every five years.

The participants were aged between 43 and 86 and the study focus was on their exercise habits and eye health.

The researchers found one in four had an active lifestyle and nearly one in four climbed more than six flights of stairs a day.

After accounting for other risk factors such as age, sex, history of arthritis, systolic blood pressure, body mass index, smoking, and education, those with a baseline active lifestyle (walking three times or more a week), were 70% less likely to develop AMD than those who did little exercise.

Also regular walkers were 30% less likely to get the disease.

Michael Knudtson, M.S., of the University of Wisconsin, and co-authors of the report do however warn that diet may also explain the findings.

The Wisconsin team say their study shows that, regardless of body mass index and other confounders, regular physical activity such as walking, might protect against the age-related eye disorder.

The study is published in the British Journal of Ophthalmology.