Philip J. Goscienski, M.D.
Humans evolved in an environment that demanded moderately intense physical activity as well as good eyesight. They needed agility, endurance and keen vision to offset the advantages that other creatures had: claws, fangs, horns and speed. As their brain power and their ability to communicate advanced rapidly over the past 100,000 years, Homo sapiens came to dominate most of the planet.
Though not as keen as that of a hawk that can identify a small rodent from hundreds of feet in the air, our ability to see has been quite adequate for survival. Defects such as cataracts, glaucoma and macular degeneration occur late enough so that there is no survival disadvantage. If any of these disorders are gene-related it simply doesn't matter. They don't interfere with our ability to propagate.
We moderns have to contend with one eye problem that never afflicted Stone Age humans: blindness due to type 2 diabetes. Most persons are not even aware that this is one of the most common causes of blindness among older adults, and that it is reaching into younger age groups as well. According to the National Eye Institute, 40-45 percent of Americans with diabetes have some form of diabetic retinopathy, the condition in which damage to the eye's blood vessels results in loss of vision.
Physical activity helps to prevent type 2 diabetes, and slows down the onset of complications in persons who already are affected. When we exercise it improves the action of insulin so that glucose (blood sugar) doesn't accumulate and damage blood vessels. In one highly publicized study more than half of persons with prediabetes, a condition in which blood sugar levels are slightly above normal, were able to avoid developing the full-blown disease. They walked at a moderate pace for 2 _ hours a week and cut back somewhat on calories.
Any form of exercise helps; it doesn't have to be organized. Taking a 10-minute walk 3 times a day is just as beneficial as walking for a half hour at a time. There are also lots of opportunities to increase physical activity throughout the day. Using the stairs instead of the elevator, parking farther away from the store, washing your car instead of driving through the car wash and working in the garden may not seem like real exercise but they all add up.
About one third of persons with diabetes are unaware that they have it but they already have one or more complications of the disease. Get your blood sugar checked if you are over age 40 or earlier if you are overweight, or are Hispanic or African-American or you have a family history of diabetes.
It's not possible to prevent other causes of blindness such as cataracts and age-related macular degeneration (AMD) with increased physical activity but there's a suggestion that resistance exercises might influence glaucoma. Working out with weights and exercise machines produces a slight reduction of the pressure within the eyeball that is characteristic of most forms of glaucoma. The effect appears to be transient, but is certainly not harmful and may have some benefits over many years.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at email@example.com.