TED | 那些漂浮在你视线中的东西是什么? —迈克尔·莫瑟

你是否会注意到自己的视线中有漂浮物？

Have you ever noticed something swimming

in your field of vision?

它看起来像是小虫或者透明液滴

It may look like a tiny worm

or a transparent blob,

但当你想要更仔细地看它的时候

它又消失了

and whenever you try to get

a closer look, it disappears,

转换视线之后

它又会出现

only to reappear

as soon as you shift your glance.

但你别去冲洗眼睛！

But don't go rinsing out your eyes!

你看的其实是一种常见现象，飞蚊症

What you are seeing is a common phenomenon

known as a floater.

科学界称之为 Muscae volitantes

The scientific name for these objects

is Muscae volitantes,

是拉丁语中飞蚊的意思

Latin for "flying flies,"

物如其名，它们有时很讨厌

and true to their name,

they can be somewhat annoying.

但它们不是真正的虫或者身外之物

But they're not actually bugs

or any kind of external objects at all.

它们就存在于你的眼球中

Rather, they exist inside your eyeball.

因为“飞蚊”会不断地变形

所以人们会觉得它们是有生命的

Floaters may seem to be alive,

since they move and change shape,

其实不是

but they are not alive.

 “飞蚊”是一种极小的物质，投影于视网膜

Floaters are tiny objects

that cast shadows on the retina,

也就是眼球后部的光敏组织

the light-sensitive tissue

at the back of your eye.

它们可能是小块组织

They might be bits of tissue,

红细胞

red blood cells,

或是蛋白质团

or clumps of protein.

由于它们悬浮于玻璃体

And because they're suspended

within the vitreous humor,

也就是眼内的胶状组织

the gel-like liquid

that fills the inside of your eye,

 “飞蚊”会随眼球而移动

floaters drift along

with your eye movements,

眼球停止转动时

它又会少许地弹动

and seem to bounce a little

when your eye stops.

 “飞蚊”大多数时候不易被察觉

Floaters may be only

barely distinguishable most of the time.

当它们靠近视网膜时，它们变得可看见

They become more visible

the closer they are to the retina,

这就相当于你把手放在吊灯下

更接近桌子时

just as holding your hand closer

to a table with an overhead light

手的阴影会更明显

will result in a more

sharply defined shadow.

 “飞蚊”也会很明显

And floaters are particularly noticeable

比如当你盯着发光的表面时

when you are looking

at a uniform bright surface,

像是空白的屏幕

like a blank computer screen,

雪

snow,

或是晴空

or a clear sky,

因为颜色一致的背景会使“飞蚊”更明显

where the consistency of the background

makes them easier to distinguish.

当看到的光越亮

瞳孔会收缩的更厉害

The brighter the light is,

the more your pupil contracts.

这就好比把许多散射的光

This has an effect similar

to replacing a large diffuse light fixture

换成一个大的聚光灯

with a single overhead light bulb,

也会使得阴影更加明显

which also makes

the shadow appear clearer.

另外也有一种视觉现象与飞蚊症类似

There is another visual phenomenon

that looks similar to floaters

但与之无关

but is in fact unrelated.

当你仰望蓝天时

If you've seen tiny dots of light

darting about

会看到小光点在快速闪动

when looking at a bright blue sky,

这被称之为谢瑞尔氏现象

you've experienced what is known

as the blue field entoptic phenomenon.

这与看到飞蚊相反

In some ways,

this is the opposite of seeing floaters.

此时,你看到的不是阴影

Here, you are not seeing shadows

而是一些移动的小开口让光进入视网膜

but little moving windows

letting light through to your retina.

这些开口是由白细胞造成的

The windows are actually caused

by white blood cells

白细胞穿梭在视网膜表面的毛细血管

moving through the capillaries

along your retina's surface.

白细胞可以大到填满整个毛细血管

These leukocytes can be so large

that they nearly fill a capillary

这导致了白细胞身前的空隙

causing a plasma space

to open up in front of them.

由于这些空隙和白细胞本身

Because the space

and the white blood cells

相比于血管中的红细胞

are both more transparent to blue light

更能让蓝光透过

than the red blood cells

normally present in capillaries,

我们因此看到小光点

we see a moving dot of light

wherever this happens,

沿着毛细血管移动

也随着脉搏而移动

following the paths of your capillaries

and moving in time with your pulse.

在理想状况下

Under ideal viewing conditions,

甚至会看到光点后有条黑尾巴

you might even see what looks

like a dark tail following the dot.

这是白细胞身后堆积的红细胞造成的

This is the red blood cells

that have bunched up behind the leukocyte.

有些科技馆中

会展览出一整屏幕的蓝光

Some science museums have an exhibit

which consists of a screen of blue light,

这会让你跟清楚的看到这一现象

allowing you to see these blue sky sprites

much more clearly than you normally would.

因为虽然每个人都会经历这些现象

While everybody's eyes experience

these sort of effects,

每个人看到的程度都不同

the number and type vary greatly.

就飞蚊症而言

In the case of floaters,

大多数会被我们的大脑所忽视

they often go unnoticed,

as our brain learns to ignore them.

但是数目异常多或者

However, abnormally numerous

大到影响视线的飞蚊

or large floaters

that interfere with vision

可能意味着你需要紧急医疗救助

may be a sign of a more serious condition,

requiring immediate medical treatment.

但是多数的眼内现象

But the majority of the time

entoptic phenomena,

比如飞蚊或者谢瑞尔氏现象

such as floaters and blue sky sprites,

只是委婉地提醒我们自认为看到的东西

are just a gentle reminder

that what we think we see

取决于我们的生理和大脑

depends just as much

on our biology and minds

就和取决于外部世界一样

as it does on the external world.