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Lights out

作者:曹侥    发布时间:2019-03-08 03:19:08    

By Nell Boyce in Washington DC BABIES who sleep with the lights on may be at greater risk of becoming short-sighted than those who sleep in the dark, a controversial study suggests. Ophthalmologists say this could explain why the problem has become so common. For more than a century, scientists have known that “near-work” such as reading or sewing can cause short-sightedness. And people seem predisposed to myopia if their parents are short-sighted. Light exposure may also play a role. Studies of baby monkeys and chicks have shown that leaving lights on all the time can affect the growth of their eyes, but until now no one had looked at this in people. So Richard Stone and his colleagues at the University of Pennsylvania Medical Center and the Children’s Hospital of Philadelphia gave a questionnaire to the parents of 479 children aged between 2 and 16. They asked whether their children slept with the light on, with a night-light, or in darkness before the age of two, when the eye grows rapidly. Of those children who had slept in darkness before the age of two, only 10 per cent had myopia at the time of the study. Of children who had slept with a night-light, 34 per cent were myopic. And as much as 55 per cent of children who had slept with a room light on were myopic (Nature, vol 399, p 113). “We haven’t proved cause and effect. A lot of work needs to be done,” says Stone. But he thinks a link to lighting may help to explain why myopia has become so common. “There were no lights three to four hundred years ago.” Some other researchers say that they welcome this new finding. “It sends a strong message to turn the lights off,” says David Guyton of Johns Hopkins Hospital in Baltimore, and a spokesman for the American Academy of Ophthalmology in San Francisco. But other experts are more sceptical. Karla Zadnik, who is conducting a long-term study of myopia in more than 3000 children at Ohio State University in Columbus, points out that the new results were not adjusted to take account of hereditary factors. “This association could be significantly confounded by whether or not they have myopic parents,

 

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