Could a lack of exposure to the outdoors cause nearsightedness (NY Times article here)? While genetics seem partially to blame, the numbers of Americans with nearsightedness have increased from 25% in the 70s to 42% today.
In the same way that we evolved with certain foods, it appears that because we evolved outdoors, our eyes are more suited to that environment:
Our genes were originally selected to succeed in a very different world from the one we live in today. Humans’ brains and eyes originated long ago, when we spent most of our waking hours in the sun. The process of development takes advantage of such reliable features of the environment, which then may become necessary for normal growth.
Most of the article focuses on making sure children spend plenty of time outdoors:
Researchers suspect that bright outdoor light helps children’s developing eyes maintain the correct distance between the lens and the retina — which keeps vision in focus. Dim indoor lighting doesn’t seem to provide the same kind of feedback. As a result, when children spend too many hours inside, their eyes fail to grow correctly and the distance between the lens and retina becomes too long, causing far-away objects to look blurry.
But what they don’t say is whether heading outside is helpful in reversing nearsightedness in adults, or whether the exposure as a child leads to any long term protection. In my case, I had amazingly good vision until I turned 21. Since then, I’ve had mild nearsightedness that seems to be getting a tiny bit worse with each passing year. I barely passed my eye exam the last time I was at the DMV.
Whatever the case, more time spent outdoors is never a bad thing. Twist my arm!