Have you ever noticed something swimming in your field of vision?
你是否會注意到自己的視線中有漂浮物?
It may look like a tiny worm or a transparent blob, and whenever you try to get a closer look, it disappears, only to reappear as soon as you shift your glance.
它看起來像是小蟲或者透明液滴,但當你想要更仔細地看它的時候它又消失了轉換視線之後它又會出現。
But don't go rinsing out your eyes!
但你別去衝洗眼睛!
What you are seeing is a common phenomenon known as a floater.
你看的其實是一種常見現象,飛蚊症。
The scientific name for these objects is Muscae volitantes, Latin for "flying flies," and true to their name, they can be somewhat annoying.
科學界稱之為Muscae volitantes,是拉丁語中飛蚊的意思物如其名,它們有時很討厭。
But they're not actually bugs or any kind of external objects at all.
但它們不是真正的蟲或者身外之物。
Rather, they exist inside your eyeball.
它們就存在於你的眼球中。
Floaters may seem to be alive, since they move and change shape, but they are not alive.
因為「飛蚊」會不斷地變形,所以人們會覺得它們是有生命的其實不是。
Floaters are tiny objects that cast shadows on the retina, the light-sensitive tissue at the back of your eye.
「飛蚊」是一種極小的物質,投影於視網膜也就是眼球後部的光敏組織。
They might be bits of tissue, red blood cells, or clumps of protein.
它們可能是小塊組織,紅細胞或是蛋白質團。
And because they're suspended within the vitreous humor, the gel-like liquid that fills the inside of your eye, floaters drift along with your eye movements, and seem to bounce a little when your eye stops.
由於它們懸浮於玻璃體,也就是眼內的膠狀組織「飛蚊」,會隨眼球而移動,眼球停止轉動時它又會少許地彈動。
Floaters may be only barely distinguishable most of the time.
「飛蚊」大多數時候不易被察覺。
They become more visible the closer they are to the retina, just as holding your hand closer to a table with an overhead light will result in a more sharply defined shadow.
當它們靠近視網膜時,它們變得可看見這就相當於你把手放在吊燈下更接近桌子時手的陰影會更明顯。
And floaters are particularly noticeable when you are looking at a uniform bright surface, like a blank computer screen, snow, or a clear sky, where the consistency of the background makes them easier to distinguish.
「飛蚊」也會很明顯比如當你盯著發光的表面時,像是空白的屏幕雪或是晴空,因為顏色一致的背景會使「飛蚊」更明顯。
The brighter the light is, the more your pupil contracts.
當看到的光越亮瞳孔會收縮的更厲害。
This has an effect similar to replacing a large diffuse light fixture with a single overhead light bulb, which also makes the shadow appear clearer.
這就好比把許多散射的光換成一個大的聚光燈也會使得陰影更加明顯。
There is another visual phenomenon that looks similar to floaters but is in fact unrelated.
另外也有一種視覺現象與飛蚊症類似但與之無關。
If you've seen tiny dots of light darting about when looking at a bright blue sky, you've experienced what is known as the blue field entoptic phenomenon.
當你仰望藍天時會看到小光點在快速閃動,這被稱之為謝瑞爾氏現象。
In some ways, this is the opposite of seeing floaters.
這與看到飛蚊相反。
Here, you are not seeing shadows but little moving windows letting light through to your retina.
此時,你看到的不是陰影,而是一些移動的小開口讓光進入視網膜。
The windows are actually caused by white blood cells moving through the capillaries along your retina's surface.
這些開口是由白細胞造成的白細胞穿梭在視網膜表面的毛細血管。
These leukocytes can be so large that they nearly fill a capillary causing a plasma space to open up in front of them.
白細胞可以大到填滿整個毛細血管,這導致了白細胞身前的空隙。
Because the space and the white blood cells are both more transparent to blue light than the red blood cells normally present in capillaries, we see a moving dot of light wherever this happens, following the paths of your capillaries and moving in time with your pulse.
由於這些空隙和白細胞本身相比於血管中的紅細胞更能讓藍光透過我們,因此看到小光點沿著毛細血管移動也隨著脈搏而移動。
Under ideal viewing conditions, you might even see what looks like a dark tail following the dot.
在理想狀況下甚至會看到光點後有條黑尾巴。
This is the red blood cells that have bunched up behind the leukocyte.
這是白細胞身後堆積的紅細胞造成的。
Some science museums have an exhibit which consists of a screen of blue light, allowing you to see these blue sky sprites much more clearly than you normally would.
有些科技館中會展覽出一整屏幕的藍光,這會讓你跟清楚的看到這一現象。
While everybody's eyes experience these sort of effects, the number and type vary greatly.
因為雖然每個人都會經歷這些現象,每個人看到的程度都不同。
In the case of floaters, they often go unnoticed, as our brain learns to ignore them.
就飛蚊症而言大多數會被我們的大腦所忽視。
However, abnormally numerous or large floaters that interfere with vision may be a sign of a more serious condition, requiring immediate medical treatment.
但是數目異常多或者大到影響視線的飛蚊,可能意味著你需要緊急醫療救助。
But the majority of the time entoptic phenomena, such as floaters and blue sky sprites, are just a gentle reminder that what we think we see depends just as much on our biology and minds as it does on the external world.
但是多數的眼內現象,比如飛蚊或者謝瑞爾氏現象,只是委婉地提醒我們自認為看到的東西取決於我們的生理和大腦,就和取決於外部世界一樣。