More Time Outside Tied To Less Nearsightedness In Children

Bookworm09 writes: For primary school children in China, spending an extra 45 minutes per day outside in a school activity class may reduce the risk of myopia, according to a new study. In some parts of China, 90% of high school graduates have nearsightedness, and rates are lower but increasing in Europe and the Middle East, the authors write. "There were some studies suggesting the protective effect of outdoor time in the development of myopia, but most of this evidence is from cross-sectional studies (survey) data that suggest 'association' instead of causality," said lead author Dr. Mingguang He of Sun Yat-sen University in Guangzhou. "Our study, as a randomized trial, is able to prove causality and also provide the high level of evidence to inform public policy."

Comments

Re:Makes sense

[ChrisMaple]

It isn't a question of strengthening. It's a question of the shape of the eye's lens and the distance from the lens to the retina.

It's a matter of controversy (although it shouldn't be) which of the two is usually misshaped in myopia.

Being outside means that most of the time the eye will be focused near infinity, and that habitual condition is what helps prevent myopia.

There are other factors involved with being outdoors in sunshine.
____Sunshine causes the generation of vitamin D. So far as I know, this does not affect myopia.
____There's proportionally more blue light outdoors. Blue is refracted more strongly (the eye is not an achromat), so to get overall better focus when there's a strong blue component in the light, the eye must focus less strongly, i.e. farther away. This improves the habitual state of the eye.

There is a claim (among the advocates of the Bates system) that muscles can be used both to focus nearer and farther away, but conventional understanding of the eye's focus mechanism is that muscles are used only to swivel the eyes and to make them focus near. Far focus is the relaxed condition.