Why do so many Chinese children wear glasses?

seneca (Expat in China)

It is nothing to do with genes. I once had about a hundred Tamil people in my charge, and only two of them wore glasses. Imagine: 98 people with good eyesight and no need to take any corrective measures. In China, though, one in three needs to wear spectacles from primary school age on.

It is because of poor lifestyle choices. Too few hours spent outdoors, too many spent in poorly lit rooms. They think the brighter the light the better for their eyes, or the light is too dim. In either case, the eyes are strained and ruined early. Eyes need good illumination with shade, so the eyes can constantly adapt.