LONDON (Reuters) - Keeping an active lifestyle can reduce the risk of developing an eye disease that is a leading cause of blindness in the elderly, researchers said on Tuesday.

Age-related macular degeneration (AMD) gradually destroys the central vision of the eye. It is linked to aging but scientists in the United States have found that physical activity such as walking and climbing stairs has a protective effect against it.

Exercise helped to reduce the odds of developing "wet," (exudative) AMD -- a form of the condition in which new blood vessels grow behind the eye causing bleeding and scarring, which leads to distorted vision and impaired sight.

The effects of physical activity were still noticed after consideration of other risk factors such as weight, blood pressure and smoking.

"Engaging in an active lifestyle or walking more...reduced the risk of developing exudative AMD over 15 years by 70 percent and 30 percent, respectively," Michael Knudtson, of the University of Wisconsin School of Medicine and Public Health, wrote in a report in the British Journal of Ophthalmology.

Knudtson and his team studied the impact of exercise on 4,000 men and women in Beaver Dam, Wisconsin over 15 years. The volunteers were between 43 and 86 years old when the study started in 1988-1990.

They were questioned about how much exercise they did and were assessed every five years. About 25 percent had an active lifestyle and nearly the same number climbed more than six flights of stairs each day.

The researchers said they could not rule out other factors but added that the report "provides evidence that a modifiable behavior, regular physical activity, such as walking, may have a protective effect for incident AMD."