I See

example of how macular degeneration affects eyesight                from afb.org

Two interesting things in one here (such a deal!): In a story that was picked up by a few news outlets, a recent study on mice seems to show that exercise, in addition to all its other known benefits, can prevent macular degeneration, in which the eye's photoreceptors degenerate and die, leading to blindness: http://www.newscientist.com/article/dn25039-exercise-could-help-prevent-agerelated-blindness.html#.Uv__8fajXgc
   That's the first interesting thing. The second is that when I researched the subject a little further, I found the following: According to a 2006 story on WebMD, "A new study suggests that regular exercise can reduce the risk of age-related macular degeneration (AMD) by up to 70%." This study followed about 4,000 men and women in a town in Wisconsin for 15 years: http://www.webmd.com/eye-health/news/20061030/exercise-may-protect-eyesight
   Another article, from 2009, reported on two studies that tracked runners and
informed that "Vigorous exercise may help prevent vision loss, according to a pair of studies from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory": http://newscenter.lbl.gov/news-releases/2009/02/09/vision-loss/
   At least now we can be sure that one way of preventing macular degeneration is through exercise. And, in another article I found, if you do get it ~ or if you know anyone who has it ~ there are some things besides taking medication that one can do: http://www.dailymail.co.uk/health/article-485170/Simple-eye-exercises-help-blind-again.html