It was reported in Nature magazine, “East Asia has been gripped by an unprecedented rise in myopia, also known as short-sightedness. Sixty years ago, 10–20% of the Chinese population was short-sighted. Today, up to 90% of teenagers and young adults are. In Seoul, a whopping 96.5% of 19-year-old men are short-sighted.” This increase in myopia has been confirmed in large studies in the US and Australia. There have been several inquiries into the possible causes, and several hours per day of reading or close computer work doesn’t seem to be the primary cause. What does seem related is not spending much time focusing one’s eyes at a distance. Because going outdoors automatically focus one’s attention on more distant objects, and generally keeps the eyes moving from one subject to another, the eyes get more exercise at focusing at a distance. People who grow up with an outdoor lifestyle rarely have myopia, but it’s still unclear if it’s the outdoors and bright light or spending a lot of time focusing at close distance that is creating the condition.
A study was mentioned where birds had their eyes covered with goggles of various sorts, and it appears that if these birds grow up with diffuse vision, as was created with some of the goggles, they lose their ability to focus well when the goggles are removed when they are fully grown adults. There are studies where children in one grade school have an hour class per day outdoors, and those in a neighboring school are kept on the regular indoor routine. The results are preliminary but the outdoor kids after one year had significantly less myopia. It appears that the developmental period for myopia is childhood, and preventive factors include having access to outdoor bright light and focusing one’s eyes at a distance.
Okay, so what’s to be done? We are told not to go outdoors because we will get skin cancer, and to protect our eyes when outdoors or we will get cataracts. Now, we are told to go outdoors to protect our eyes from becoming near-sighted; at least this seems to be true for children when their vision is developing.
What seems obvious is that we gain a lot by getting outdoors every day for over an hour. If we walk with a partner, we get some pleasant social interaction, and we get some exercise, and now we discover we get some eye improvements. I would suspect that when walking we should protect our eyes from direct sunshine by wearing a billed hat, but sunglasses in addition to the hat may not be essential, and really dark sunglasses would probably be counter productive.
Go for a walk every day, smile at the sky and enjoy a friendly companion. Walking a mile to school or work would be perfect.