Two studies by the U.S. Department of Energy's Lawrence Berkeley National Laboratory tracked approximately 41,000 runners for more than seven years.
"The studies suggest that people can perhaps lessen their risk for these diseases by taking part in a fitness regimen that includes vigorous exercise," study leader Paul Williams said in a statement.
A cataract -- a cloudy opacity of the eye lens -- is the leading cause of blindness and more than one-half of U.S. adults 65 and older suffer from some form of cataracts. Age-related macular degeneration -- damage to the retina -- is the leading cause of irreversible vision loss in older white Americans, affecting 28 percent of people age 75 and older, Williams said.
Williams analyzed data collected in the National Runners' Health Study, which he established in 1991 to determine the health benefits of running.
He tracked some 29,000 male runners and 12,000 female runners for more than seven years and of these 733 men reported being diagnosed with cataracts. Too few women reported cataracts to track.
The studies, published in Investigative Ophthalmology and Visual Science, found men who ran more than 5.7 miles per day had a 35 percent lower risk of developing cataracts than men who ran less than 1.4 miles per day.