Excersizing at least 3 times per week can slow the progression of age-related macular degeneration.
The Public Health Agency of Canada recommends:
2 ½ hours moderate to vigorous intensity physical activity per week
60 minutes of moderate to vigorous intensity physical activity per day
Seddon, J., J. Cote, N. Davis, and B. Rosner. 2003. Progression of ARM associated with BMI, waist circumference and waist, hip ratio. Arch ophthalmol 121: 785-92.