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Bright light outdoors is good — but stay in the shade to avoid skin cancer.

The #myopia boom http://www.nature.com/news/the-myopia-boom-1.17120 Was attributed to books; now epidemiological & lab evidence suggests not enough daylight for kids

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“Rose’s team tried to eliminate any other explanations for this link — for example, that children outdoors were engaged in more physical activity and that this was having the beneficial effect. But time engaged in indoor sports had no such protective association; and time outdoors did, whether children had played sports, attended picnics or simply read on the beach. And children who spent more time outside were not necessarily spending less time with books, screens and close work. “We had these children who were doing both activities at very high levels and they didn’t become myopic,” says Rose. Close work might still have some effect, but what seemed to matter most was the eye’s exposure to bright light.

See the light

Some researchers think that the data to support the link need to be more robust. Most epidemiological studies have estimated children’s time outdoors from questionnaires — but Christine Wildsoet, an optometrist at the University of California, Berkeley, says that such data should be treated with caution. In a small, pilot study of wearable light sensors, she found that people’s estimates often do not match up with their actual exposure. And Ian Flitcroft, a myopia specialist at Children’s University Hospital in Dublin, questions whether light is the key protective factor of being outdoors. He says that the greater viewing distances outside could affect myopia progression, too. “Light is not the only factor, and making it the explanation is a gross over-simplification of a complex process,” he says.

Yet animal experiments support the idea that light is protective. Researchers first demonstrated this in chicks, a common lab model for studying vision. By fitting chicks with goggles that alter the resolution and contrast of incoming images, it is possible to induce the development of myopia while raising the birds under controlled conditions in which only light intensity is changed. In 2009, Regan Ashby, Arne Ohlendorf and Frank Schaeffel from the University of Tübingen’s Institute for Ophthalmic Research in Germany showed that high illumination levels — comparable to those encountered outside — slowed the development of experimentally induced myopia in chicks by about 60% compared with normal indoor lighting conditions. Researchers elsewhere have found similar protective effects in tree shrews and rhesus monkeys.”

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