Interesting article in Treehugger posits that exploding global rates of myopia – nearsightedness – might be caused by children’s lack of exposure to daylight.
Here’s the punchline:
While some researchers think more data is needed to confirm the theory, animal experiments further support the idea that being outdoors, and exposure to the light that comes with it, is protective. The leading hypothesis, explains Dolgin, is that light stimulates the release of dopamine in the retina, and this neurotransmitter in turn blocks the elongation of the eye during development.
Based on epidemiological studies, Ian Morgan, a myopia researcher at the Australian National University in Canberra, recommends that children spend three hours per day under light levels of at least 10,000 lux for protection against the condition. Ten thousand lux would be about the amount of light one would get from beneath a shady tree on a bright summer day (and wearing sunglasses). For comparison, a well-lit schoolroom or office is generally under 500 lux.