近视是怎么回事

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.

有些人在房间的一头看另一头的数字时钟没有问题，而另一些人却需要眼镜或隐形眼镜才能在三英寸以外看清同一个时钟。这当然是不公平的，但近视的人已经学会接受这一现实。近视的人也不只是少数。事实上，超过40%的美国人患有近视，根据美国眼科研究所的数据，这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.

近视一点也不好玩。梅奥诊所表示，许多近视眼患者视力模糊，需要眯着眼睛才能看清楚，眼睛疲劳还会导致头痛。

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.

由于遗传因素，有些人更容易近视，但这远远不是唯一的近视因素。根据世界卫生组织的数据，如果人们花大量时间呆在室内或在短距离内进行许多活动(如阅读或看电视)，则更容易近视。

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.

根据美国眼科研究所的数据，大多数近视患者的眼球都异常长。因此，图像聚焦在视网膜(感知光线的组织层)前面，而不是视网膜上。这使得人们近距离看得很清楚，但从远处就看不清楚。

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.

梅奥诊所指出，如果角膜曲线过于陡峭，人们也可能患上近视。角膜是眼睛的外层，帮助眼睛聚焦光线。当角膜有平滑的曲线时，它会将任何射入的光线直接射入视网膜，从而产生聚焦良好的图像。另一方面，如果曲线太陡，光只会发送到视网膜前面，使离人眼不够近的物体产生模糊的图像。

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

梅奥诊所(Mayo Clinic)表示，远视的人则有相反的问题，他们的眼球异常短，角膜曲率不够。