近視是怎么回事

Some people have no problem reading a digital clock from all the way across a room, while others need glasses or contact lenses to be able to read the same clock from more than three inches away. It certainly isn't fair, but it is a reality that nearsighted people have learned to live with. There aren't only a few nearsighted people, either. In fact, more than 40% of Americans are nearsighted, and this percentage is only increasing each year, according to the National Eye Institute.

有些人在房間的一頭看另一頭的數(shù)字時(shí)鐘沒有問題，而另一些人卻需要眼鏡或隱形眼鏡才能在三英寸以外看清同一個(gè)時(shí)鐘。這當(dāng)然是不公平的，但近視的人已經(jīng)學(xué)會(huì)接受這一現(xiàn)實(shí)。近視的人也不只是少數(shù)。事實(shí)上，超過40%的美國(guó)人患有近視，根據(jù)美國(guó)眼科研究所的數(shù)據(jù)，這一比例每年都在增加。

Being nearsighted is far from fun. Many nearsighted people struggle with blurry vision, the need to squint in order to see clearly, and headaches due to eyestrain, says the Mayo Clinic.

近視一點(diǎn)也不好玩。梅奧診所表示，許多近視眼患者視力模糊，需要瞇著眼睛才能看清楚，眼睛疲勞還會(huì)導(dǎo)致頭痛。

Some people are more prone to nearsightedness due to genetics, but that is far from the only risk factor. According to the World Health Organization, people are more likely to become nearsighted if they spend a lot of time indoors or perform many activities (such as reading or watching television) from a short distance.

由于遺傳因素，有些人更容易近視，但這遠(yuǎn)遠(yuǎn)不是唯一的近視因素。根據(jù)世界衛(wèi)生組織的數(shù)據(jù)，如果人們花大量時(shí)間呆在室內(nèi)或在短距離內(nèi)進(jìn)行許多活動(dòng)(如閱讀或看電視)，則更容易近視。

According to the National Eye Institute, most nearsighted people have abnormally long eyeballs. Because of this, images are focused in front of the retina (the layer of tissue that senses light) instead of on the retina. This causes a person to see well from up close, but poorly from a distance.

根據(jù)美國(guó)眼科研究所的數(shù)據(jù)，大多數(shù)近視患者的眼球都異常長(zhǎng)。因此，圖像聚焦在視網(wǎng)膜(感知光線的組織層)前面，而不是視網(wǎng)膜上。這使得人們近距離看得很清楚，但從遠(yuǎn)處就看不清楚。

The Mayo Clinic notes that people can also become nearsighted if their cornea has too steep of a curve. The cornea is the outer layer of the eye that helps your eye focus light. When the cornea has a smooth curve, it will send any incoming light directly onto the retina, resulting in a well-focused image. If the curve is too steep, on the other hand, the light will only be sent in front of the retina, creating a blurry image for objects that aren't close enough to the person's eyes.

梅奧診所指出，如果角膜曲線過于陡峭，人們也可能患上近視。角膜是眼睛的外層，幫助眼睛聚焦光線。當(dāng)角膜有平滑的曲線時(shí)，它會(huì)將任何射入的光線直接射入視網(wǎng)膜，從而產(chǎn)生聚焦良好的圖像。另一方面，如果曲線太陡，光只會(huì)發(fā)送到視網(wǎng)膜前面，使離人眼不夠近的物體產(chǎn)生模糊的圖像。

Farsighted people have the opposite problem, with abnormally short eyeballs or corneas with not enough curvature, says Mayo Clinic.

梅奧診所(Mayo Clinic)表示，遠(yuǎn)視的人則有相反的問題，他們的眼球異常短，角膜曲率不夠。