中英文稿

你是否會注意到自己的視線中有漂浮物？?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(zhuǎn)換視線之后 它又會出現(xiàn)?但你別去沖洗眼睛！?你看的其實是一種常見現(xiàn)象，飛蚊癥?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?但它們不是真正的蟲或者身外之物?它們就存在于你的眼球中?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?“飛蚊”是一種極小的物質(zhì)，投影于視網(wǎng)膜?也就是眼球后部的光敏組織?它們可能是小塊組織?紅細胞?或是蛋白質(zhì)團?由于它們懸浮于玻璃體?也就是眼內(nèi)的膠狀組織?“飛蚊”會隨眼球而移動?眼球停止轉(zhuǎn)動時 它又會少許地彈動?“飛蚊”大多數(shù)時候不易被察覺?當它們靠近視網(wǎng)膜時，它們變得可看見?這就相當于你把手放在吊燈下 更接近桌子時?手的陰影會更明顯?“飛蚊”也會很明顯?比如當你盯著發(fā)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?當看到的光越亮 瞳孔會收縮的更厲害?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?另外也有一種視覺現(xiàn)象與飛蚊癥類似?但與之無關(guān)?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(xiàn)象?這與看到飛蚊相反?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(wǎng)膜?這些開口是由白細胞造成的?白細胞穿梭在視網(wǎng)膜表面的毛細血管?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?由于這些空隙和白細胞本身?相比于血管中的紅細胞?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?在理想狀況下?甚至會看到光點后有條黑尾巴?這是白細胞身后堆積的紅細胞造成的?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(xiàn)象?因為雖然每個人都會經(jīng)歷這些現(xiàn)象?每個人看到的程度都不同?就飛蚊癥而言

大多數(shù)會被我們的大腦所忽視?但是數(shù)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(yī)療救助?但是多數(shù)的眼內(nèi)現(xiàn)象?比如飛蚊或者謝瑞爾氏現(xiàn)象?只是委婉地提醒我們自認為看到的東西?取決于我們的生理和大腦?就和取決于外部世界一樣

Have you ever noticed something swimming in your field of vision??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.?But don't go rinsing out your eyes!?What you are seeing is a common phenomenon?known as a floater.?The scientific name for these objects is Muscae volitantes,?Latin for "flying flies,"?and true to their name, they can be somewhat annoying.?But they're not actually bugs or any kind of external objects at all.?Rather, they exist inside your eyeball.?Floaters may seem to be alive, since they move and change shape,?but they are not alive.?Floaters are tiny objects that cast shadows on the retina,?the light-sensitive tissue at the back of your eye.?They might be bits of tissue,?red blood cells,?or clumps of protein.?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.?Floaters may be only barely distinguishable most of the time.?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.?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.?The brighter the light is, the more your pupil contracts.?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.?There is another visual phenomenon that looks similar to floaters?but is in fact unrelated.?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.?In some ways, this is the opposite of seeing floaters.?Here, you are not seeing shadows?but little moving windows letting light through to your retina.?The windows are actually caused by white blood cells?moving through the capillaries along your retina's surface.?These leukocytes can be so large that they nearly fill a capillary?causing a plasma space to open up in front of them.?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.?Under ideal viewing conditions,?you might even see what looks like a dark tail following the dot.?This is the red blood cells that have bunched up behind the leukocyte.?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.?While everybody's eyes experience these sort of effects,?the number and type vary greatly.?In the case of floaters,?they often go unnoticed, as our brain learns to ignore them.?However, abnormally numerous?or large floaters that interfere with vision?may be a sign of a more serious condition, requiring immediate medical treatment.?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.