纽约时报：为什么现在近视的人那么多？

译者 wu200506

WHY is nearsightedness so common in the modern world? In the early 1970s, 25 percent of Americans were nearsighted; three decades later, the rate had risen to 42 percent, and similar increases have occurred around the world.

为什么近视在全球如此常见？早在二十世纪七十年代，25%的美国人患有近视。30年之后，这个比例上升到42%，并且在全球范围内也有这个上升趋势。

There is significant evidence that the trait is inherited, so you might wonder why our myopic ancestors weren’t just removed from the gene pool long ago, when they blundered into a hungry lion or off a cliff. But although genes do influence our fates, they are not the only factors at play.

最重要的原因是该特征是遗传的。因此，你也许会想，为什么我们近视的祖先不能从淘汰此基因，当他们无意间碰到一只饥饿的老虎或者不小心掉到悬崖里，但是，尽管这些基因影响着我们的命运，但它不是在近视形成的过程中的唯一因素。

In this case, the rapid increase in nearsightedness appears to be due to a characteristic of modern life: more and more time spent indoors under artificial lights.

既然这样，快速的近视增长率其主要原因主要是由于现代生活的特征所引起的：人们打室内人造光源下的时间越来越长。

Our genes were originally selected to succeed in a very different world from the one we live in today. Humans’ brains and eyes originated long ago, when we spent most of our waking hours in the sun. The process of development takes advantage of such reliable features of the environment, which then may become necessary for normal growth.

我们的基因原始的选择不同于现在我们居住的时代一样。人类的大脑和眼睛很早就产生了，当我们花费大量的时间在太阳下行走。这种进化过程利用的环境的可靠因素，这可能是其正常发展的必要条件。

Researchers suspect that bright outdoor light helps children’s developing eyes maintain the correct distance between the lens and the retina — which keeps vision in focus. Dim indoor lighting doesn’t seem to provide the same kind of feedback. As a result, when children spend too many hours inside, their eyes fail to grow correctly and the distance between the lens and retina becomes too long, causing far-away objects to look blurry.

研究人员认为，室外光线能帮助孩子在晶状体和虹膜之间---能保持视野更加清晰---维持准确的距离。晦暗的室内光线似乎不能提供这中功效。因此，当孩子们在室内呆的时间很长时，晶状体和虹膜之间就变得更长，就不是不那么准确区分物体的距离，使远处的物体变得模糊。

One study published in 2008 in the Archives of Ophthalmology compared 6- and 7-year-old children of Chinese ethnicity living in Sydney, Australia, with those living in Singapore. The rate of nearsightedness in Singapore (29 percent) was nearly nine times higher than in Sydney. The rates of nearsightedness among the parents of the two groups of children were similar, but the children in Sydney spent on average nearly 14 hours per week outside, compared with just three hours per week in Singapore.

一份2008年发表在《眼科学文献》的研究报告对生活在澳大利亚悉尼的6至7岁的华裔儿童和新加坡儿童进行了比较。新加坡近视的比率为29%，要比悉尼的数字高9倍。这两组孩子中，父母近视的比率是类似的，但是悉尼儿童平均每周呆在户外的时间约14小时，新加坡的儿童每周只有3小时

Similarly, a 2007 study by scholars at Ohio State University found that, among American children with two myopic parents, those who spent at least two hours per day outdoors were four times less likely to be nearsighted than those who spent less than one hour per day outside.

2007年俄亥俄州立大学多名学者的研究也得到类似的结论，在父母都近视的美国儿童中，每天呆在户外不少于2小时的儿童患近视的可能要比每天呆在户外不足1小时的要低4倍多。

In short, the biological mechanism that kept our vision naturally sharp for thousands of sunny years has, under new environmental conditions, driven visual development off course. This capacity for previously well-adapted genes to be flummoxed by the modern world can account for many apparent imperfections. Brain wiring that effortlessly recognizes faces, animals and other symmetrical objects can be thrown off by letters and numbers, leading to reading difficulties. A restless nature was once helpful to people who needed to find food sources in the wild, but in today’s classrooms, it’s often classified as attention deficit hyperactivity disorder. When brains that are adapted for face-to-face social interactions instead encounter a world of e-mail and Twitter — well, recent headlines show what can happen.

简 而言之，数万年来适应太阳光的视力敏捷的生物机制在新环境下已经偏离了发展轨道。之前基因能较好适应环境的能力已经被现代世界新的状况给搞乱了，这也是许 多明显的缺陷产生的原因。能轻松识别脸部、动物和其它对称物体的大脑线路已经落伍了，现在面对的是字母和数字，因为导致了阅读的困难。那种不满足的个性曾 是野外寻找食物来源所必须的能力，在如今的课堂上则被归类于注意缺陷多动障碍（简称为多动症）。曾经适应面对面交流的大脑现在也不得不对着email 和twitter了，最近头条会让你知道最近有哪些新闻。

Luckily, there is a simple way to lower the risk of nearsightedness, and today, the summer solstice — the longest day of the year — is the perfect time to begin embracing it: get children to spend more time outside.

幸运的是，还有简单的方法能够降低近视的概率，今天是夏至，一年中白天最长的一天，我们该好好利用了，让你的孩子多点时间呆在户外吧。

Parents concerned about their children’s spending time playing instead of studying may be relieved to know that the common belief that “near work” — reading or computer use — leads to nearsightedness is incorrect. Among children who spend the same amount of time outside, the amount of near work has no correlation with nearsightedness. Hours spent indoors looking at a screen or book simply means less time spent outside, which is what really matters.

担 心孩子把时间用来玩而不是学习的父母也许会感到欣慰，因为“近距离工作”（即阅读或使用电脑）会导致近视的传统观点是不正确的。花同样时间呆在户外的儿童 中，近距离工作的时间与近视没有相关性。不过呆在室内对着屏幕或者看书几个小时就没有那么多的时间去户外了，这才是问题所在。

This leads us to a recommendation that may satisfy tiger and soccer moms alike: if your child is going to stick his nose in a book this summer, get him to do it outdoors.

这有一条对虎妈和单亲妈妈们都实用的建议：如果你的孩子打算读书度过这个夏天，那就让他们在室外看书吧。

Sandra Aamodt, a former editor in chief of Nature Neuroscience, and Sam Wang, an associate professor of molecular biology and neuroscience at Princeton University, are the authors of the forthcoming “Welcome to Your Child’s Brain: How the Mind Grows from Conception to College.”

《自然-神经科学》的前任主编桑德拉。阿茂德和来自普林斯顿大学的分子生物学和神经科学萨姆·王副教授在他们的即将出版的书中《欢迎你的孩子的大脑：心灵成长如何从构想到学院》