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Being nearsighted is far more common than it once was. The prevalence of myopia, the condition's medical name, in Americans has soared by 66 percent since the early 1970s, according to a 2009 study by the National Eye Institute; in China and other East Asian countries, as many as 90 percent of recent high school graduates are thought to be nearsighted. 近视比以前普遍多了。据美国国家眼科研究所2009年的一项研究显示，自20世纪70年代初，美国人近视的比例飙升了66%；而在中国和其他东亚国家，高达90%的高中毕业生被视为近视。 Myopia results when eyeballs are longer than normal, changing the angle at which light enters the eye and therefore the ability to focus on distant objects. 当眼球比正常情况下长时，近视就会发生，改变光线进入眼睛的角度，从而改变眼睛聚焦远处物体的能力。 The disorder involves a complex interplay of genetics and environment and usually begins before adolescence, when the eye is growing, but it can worsen in early adulthood. 这种疾病涉及了遗传和环境的复杂相互作用，通常发生在青春期之前，那时候眼睛还在成长，但在成年初期可能会恶化。 | 
