How do glasses help us see? - Andrew Bastawrous and Clare Gilbert

翻译人员: Shufang Liu 校对人员: Jiawei Ni

Almost 2000 years ago,

大约2000年前

the Roman philosopher Seneca peered at his book through a glass of water.

罗马哲学家塞涅卡（Seneca）透过一杯水撇看了他的书

Suddenly, the text below was transformed.

突然，下面的文字变形了

The words magically became clear.

文字神奇地变得很清楚

But it wasn't until a millennium later that that same principle

但是直到一千年之后，同样的原理

would be used to create the earliest glasses.

被用来创造出最早的眼鏡

Today, glasses can help millions of people with poor vision

今天，眼鏡能够帮助数百万的视力差的人们

due to uncorrected refractive errors.

归咎于未经矫正的屈光不正。

The key to understanding what that means lies with the term refraction,

理解这代表什么的关键取决于这个术语折光能力，

the ability of a transparent medium, like glass,

一个透明媒体的能力，如玻璃

water,

水

or the eye to change the direction of light passing through it.

或者眼睛，当光穿过它时，来改变光的方向

The eye has two main refractive surfaces:

眼睛有两个主要的折射面

the cornea and the lens.

角膜和晶状体

Ideally, these surfaces work together

理想情况下，这些面一起工作

to refract light in a way that accurately focuses light onto the retina,

在某种程度上来折射光，准确地把光聚焦于视网膜

the layer of light-sensitive tissue at the back of the eye

视网膜是在眼睛后面，感光的一层薄膜

that works with the brain to give rise to vision.

它和大脑一起工作来提升視力

But many people develop refractive errors,

但是很多人产生了屈光不正。

either during childhood as their eyes are growing,

或者在孩童时期当他们眼睛成长时，

or in later life as their eyes age.

或者在在后面的时期当他们的眼睛变老

Imperfections in the cornea and lens

角膜和晶状体的缺陷

cause refracted light to be focused in front of or behind the retina,

导致折射的光聚焦于视网膜的前面或者后面

making images appear blurry.

使得图像显示模糊

People with refractive errors can still see color,

有屈光不正的人仍然能够看到颜色

movement,

移动

and light,

和光

but the details of what they're looking at are out of focus.

但是他们正在的看的细节是模糊不清的

People experience refractive errors in different ways,

人们通过不同的方式经历着屈光不正，

owing to differences in their eyes.

由于他们的眼睛内部的不同

In some, light refracts too much,

在有些眼睛里，光折射太多

and in others, too little.

而在另外一些，太少

Eyes with a focal point in front of the retina are called myopic,

在视网膜前面有聚焦点的眼睛被称为近视

or short-sighted.

或者短视

They can see close objects clearly,

他们能清楚地看到近的物体，

but those far away are out of focus.

但是看远的就很模糊

But when the focus point is behind the retina,

但是当聚焦点在视网膜后面的话，

people are hyperopic, or long-sighted.

这些人是远视的

For them, objects close up are unfocused,

对他们来讲，近的物体是模糊的。

but distant objects are crystal clear.

但是远距离的物体十分清楚。

Finally, some people have a cornea with a non-spherical shape

最后，有些人有非球状的角膜

that causes astigmatism,

这导致散光

a form of out-of-focus vision that makes all objects seem blurred,

这种焦点没对准的视力使得所有的物体都是模糊的，

whether close or far.

不论是近的还是远的。

As we age, our eyes face new challenges.

随着我们变老，我们的眼睛面临着新的挑战。

When we're young, the lens of the eye is flexible

当我们年轻时，眼睛的晶状体是有弹性的

and can change shape to bring images into focus,

可以改变形状使得图像在焦距内

something called accommodation.

某种东西叫做适应性调节

This keeps objects in focus when we shift our gaze from far to near.

当我们从远到近移动我们的注视时，这使得物体保持聚焦

But as we get older, the lens becomes less flexible,

但是随着我们变得老，晶状体变得弹性差些

and can't change shape when we want to look at near objects.

当我们想看近的物体时并不能改变形状

This is called presbyopia,

这个叫做老花眼（远视眼）

and it affects adults starting around the age of 40 years.

从40岁开始影响成年人

Myopia,

hyperopia,

近视

远视

astigmatism,

散光

and presbyopia.

老花眼

Each of these is a refractive error.

每一个都是屈光不正

Nowadays we can fix them all with glasses or contact lenses,

现在我们可以校正他们用眼镜或者隐形眼镜

which work by refocusing light so it strikes the retina precisely.

重新聚焦光，从而使得光精确地能到达视网膜

It's even possible to correct vision with surgery

甚至可以通过外科手术来矫正视力

using lasers that change the shape of the cornea

通过激光来改变角膜的形状

and alter its refractive properties.

和改变它的折光特性。

But glasses remain the most popular.

但是眼镜仍然是最流行的

By using carefully crafted lenses

通过小心地运用精心制作的镜片

to steer light to exactly the right spot on the retina,

来控制光线准确的定位在视网膜

a person's clear vision can be restored.

一个人的清楚的视力是可以被恢复的

We've come a long way since Seneca's discovery

我们已经走了很长的路，从塞涅卡（Seneca）的发现

and the crude glasses of yesteryear.

和不久以前的未经加工的眼镜.

In 1727, a British optician named Edward Scarlett

在1727年，一个名叫Edward Scarlett英国的眼镜商

developed the modern style of glasses

开发了现代风格的眼镜

which are kept in place with arms which hook over each ear.

通过镜臂钩架在耳朵上来固定

Today's glasses take their inspiration from that design,

现在的眼镜从那个设计取得灵感

but they're also much more precise and personal.

但是他们也更加精准和个性化

Each pair is tailored for an individual to bring out their unique powers of sight.

每对眼镜为每一个人定制而显示出他们独特的视觉能力

So if you're one of the 500 million people with a problem with close or far vision,

所以如果你是5亿有近视或者远视问题的人之一

or both,

或者及近视又远视

there's a pair of glasses out there waiting to reveal a whole new world

有一对眼镜等着呈现模糊景象背后的

that's hiding in plain view.

一个全新的世界