In sometimes subtle ways we are creating a civilization that is incompatible with some of our genetic inheritance. Some researchers working in Australia and Singapore were able too show that children who spend less time outdoors get myopia at higher rates.
The team looked only at children of Chinese ethnicity, to rule out genetic differences between races as an explanation for higher myopia rates in certain countries.
The result? On average the children in Sydney spent nearly 14 hours per week outside, and only 3 per cent developed myopia. In contrast, the children in Singapore spent just 3 hours outside, and 30 per cent developed myopia. Once again, close work had a minimal influence; the Australian children actually spent more time reading and in front of their computers than the Singaporeans (Archives of Ophthalmolology, vol 126, p 527).
Possibly the light hitting the eyeballs regulates their growth and insufficient light during development causes the eyeballs to grow incorrectly. The article describes the results of other research on causes of myopia. Click through if you have an interest.
Singapore with its dense population and high rise living strikes me as the sort of place where humans experience an environment far from our ancestral environments. Kids can't easily play outside when they live in a high rise. Cities really aren't good for raising children. By contrast, I feel fortunate that where I grew up I walked out the door and I was on a big plot of land bordering a forest and farm land. I could get thoroughly dirty (an opportunity rarely missed). The dirt probably helped my immune system develop from all the microbes it came into contact with. Plus, summers were spent outside for very long hours. Lots of vitamin D and light hitting my eyeballs.