在光线暗处看书真的对眼睛有害吗?

Mom always told us we'd go blind if we read in the dark. Does science back her up? Jim Sheedy, a doctor of vision science and director of the Vision Performance Institute at Oregon's Pacific University, sets his sights on the truth.

妈妈总是告诉我们如果我们在暗处看书会弄坏眼睛。这种说法有科学依据吗？且听俄勒冈太平洋大学(Pacific University)视觉功能学院(Vision Performance Institute)所长、视觉科学医生吉姆?希迪(Jim Sheedy)为我们揭示真相。

Dark Matter

暗处阅读

Turns out, our parents were wrong. 'There is no reason to believe nor evidence to support that any long-term damage to the eyes or change in the physiology to the eyes can be caused by reading in the dark,' Dr. Sheedy says。

原来，我们的父母是错的。希迪博士说：“我们没有理由认为，也没有证据证明，在暗处阅读会造成眼睛的长期损害，或引起眼睛的生理变化。”

That is not to say that nocturnal page-turning won't lead to discomfort or fatigue。

但这并不意味着在夜间昏暗光线下看书不会引起不适和疲劳。

The lack of light will cause the pupils to dilate, resulting in a smaller depth of field -- the distance between the nearest and farthest object that the eye considers to be in focus. Dr. Sheedy says the added effort to change focus (called the eye's accommodative system) and the effort to change the angle of the lines of sight between the two eyes (called the vergent system) will likely make your eyes feel tired and your body spent. But, of course, that's often the object of reading under the covers。

光线不足会引起瞳孔扩张，导致景深变小，即眼睛能聚焦的最近和最远的物体之间的距离变小。希迪博士说，费力地去变焦(通通过眼睛的调节系统)和费力去地改变两眼之间的视角(通过眼睛的收缩系统)可能会使你的眼睛和身体感到疲倦。当然，这通常是在被窝里看书的后果。

Seeing Clearly

看清楚

Dr. Sheedy says he assures his students that there isn't enough evidence to argue that what you do with your eyes leads to myopia (nearsightedness)： 'The predominant determinant of myopia is genetics.' No link to long-term damage has ever been conclusively shown, says Dr. Sheedy. 'It's an old tale, a ploy used by moms to get kids to go to sleep when they wanted them to,' he says。

希迪博士说他告诉他的学生现在还没有足够的证据能说明用眼习惯会导致近视：“近视的主要决定因素是遗传。”他说并没有确凿的证据证明长期损害跟近视之间存在关联。希迪博士说：“这只是一个古老的传说，是妈妈们希望孩子们去睡觉时常用的一个说辞。”

Electronic Age

电子时代

Reading on a tablet device won't damage your eyes, Dr. Sheedy says. His team has studied various fonts, computer displays and pixel resolutions, and found the difference in effect on the eye between reading e-ink and the printed word to be negligible。

希迪博士说，在平板设备上阅读文字不会伤害眼睛。他的团队对各种字体、电脑显示器和像素分辨率进行了研究，发现阅读电子读物和印刷文字对眼睛影响的差异是可以忽略不计的。

He adds that pixel density and screen resolution have reached the point at which the eye doesn't know which it is seeing. So if reading a printed book in dim light is fine, so is reading a Kindle or iPad。

他补充说，像素密度和屏幕分辨率已经发展到了让眼睛分辨不出电子读物和印刷文字之间差异的程度。如果在昏暗的光线下阅读印刷书籍没什么问题的话，在Kindle或iPad上阅读也不会有问题。

Moving from Dark to Light

从暗处到亮处

The eyes adapt quickly when going to the light -- emerging from a tunnel into the sun, say -- but going to the dark 'requires the regeneration of photo pigments, and that takes some time to reach full dark-adaptation,' says Dr. Sheedy。

希迪博士说，从暗处到亮处时眼睛适应起来非常快，比如从隧道里出来重见天日时，但从亮处到暗处时“需要新生成光色素，因此需要一些时间来完全适应黑暗”。

Adjusting to the dim light next to your bed should only take seconds. But when going from bright light to maximum darkness, studies have shown, eye sensitivity continues to change for up to 25 minutes, he says。

他说，你对自己床边暗光灯的光线的适应只需要几秒钟的时间。但有研究表明，如果从亮如白昼转到漆黑一片，眼睛的感光度要持续变化长达25分钟的时间。

Just ask a pirate。

问问海盗吧

'Ever wonder why a pirate wears patches? It's not because he was wounded in a sword fight,' says Dr. Sheedy. Seamen must constantly move between the pitch black of below decks and the bright sunshine above。

希迪博士说：“想知道为什么海盗总是戴着眼罩吗？这并不是因为他在剑战中受了伤。”真正的原因是水手必须经常在漆黑的甲板下和明亮的阳光下这两处地方之间变换位置。

Smart pirates 'wore a patch over one eye to keep it dark-adapted outside.' Should a battle break out and the pirate had to shimmy below, he would simply switch the patch to the outdoor eye and he could see in the dark right away -- saving him 25 minutes of flailing his cutlass about in near blindness。

聪明的海盗“在一只眼睛上戴着眼罩，就能保证有一只眼睛始终能适应黑暗。”如果战斗爆发，海盗必须转战到甲板下面，他只需要把眼罩换到另一边，就可以马上在黑暗中恢复视力──这样一来他就不用在近乎失明的情况下挥剑战斗25分钟了。