Scientists blame surging Asian myopia rates on too much time spent indoors

Myopia isn't an infectious disease, but it has reached nearly epidemic proportions in parts of Asia.

In Taiwan, for example, the percentage of seven-year-old children suffering from nearsightedness rose from 5.8 per cent in 1983 to 21 per cent in 2000. An incredible 81 per cent of Taiwanese 15-year-olds are myopic.

The prevalence of high myopia, an extreme form of the disorder, has more than doubled in Asia since the 1980, and children who suffer myopia early in life are more likely to progress to high myopia. High myopia is a risk factor for such serious problems as retinal detachment, glaucoma, early onset cataracts and blindness.

The explosion of myopia is a serious public health concern and doctors have struggled to identify the source of the problem. A variety of risk factors has been linked to the disorder: Frequent reading, participation in sports, television watching, protein intake and depression. When each risk factor was isolated, however, its overall effect on myopia rates seemed to be fairly minimal.

But researchers believe they are now closing in on a primary culprit: Too much time indoors. 

In 2008 orthoptics professor Kathryn Rose found that only 3.3 per cent of six and seven-year-olds of Chinese descent living in Sydney, Australia, suffered myopia, compared with 29.1 per cent of those living in Singapore. The usual suspects, reading and time in front of an electronic screen, could not account for the discrepancy.

The Australian cohort read a few more books and spent slightly more time in front of the computer, but the Singaporean children watched a little more television. On the whole, the differences were small and probably cancelled each other out. The most glaring difference between the groups was that the Australian children spent 13.75 hours per week outdoors compared with 3.05 hours for children in Singapore.