爲什麼近視的人越來越多了?

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.
近視比以前普遍多了。據美國國家眼科研究所2009年的一項研究顯示，自20世紀70年代初，美國人近視的比例飆升了66%；而在中國和其他東亞國家，高達90%的高中畢業生被視爲近視。

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.
當眼球比正常情況下長時，近視就會發生，改變光線進入眼睛的角度，從而改變眼睛聚焦遠處物體的能力。

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.
這種疾病涉及了遺傳和環境的複雜相互作用，通常發生在青春期之前，那時候眼睛還在成長，但在成年初期可能會惡化。

Some experts connect the elevated rates of myopia to the many hours young people stare at computers and other screens. But a recent study published in JAMA Ophthalmology suggests that a greater factor may be a side effect of all that screen-watching — it's keeping children inside.
一些專家認爲近視率升高與年輕人長時間盯着電腦和其他屏幕有關。但最近發表在《美國醫學會眼科雜誌》上的一項研究表明，更重要的因素可能是使孩子長時間盯着屏幕看的副作用是讓孩子呆在了室內。

This new study joins a growing body of research indicating that a lack of direct sunlight may reshape the human eye and impair vision.
越來越多的研究表明，缺少與陽光的接觸可能會改變眼睛的形狀，而損害視力。

Strong correlations were found between current eyesight and volunteers' lifetime exposure to sunlight, above all UVB radiation (which is responsible for burning).
研究發現，志願者目前的視力與其暴露在陽光下（尤其是導致灼傷的中波紫外線輻射）的時長有很強的相關性。

Those who had gotten the most sun, particularly between the ages of 14 and 19, were about 25 percent less likely to have developed myopia by middle age.
那些經常曬太陽的人，尤其是14歲到19歲之間的人，中年近視的可能性要低25%。

Exposure to sunlight up to the age of 30 also conferred a protective benefit.
30歲之前曬曬太陽也有保護作用。

This relationship held true even when the researchers controlled for education as a marker primarily of time spent reading and gazing at screens.
即使研究人員把教育作爲閱讀和盯着屏幕看的主要原因，這種關係仍然成立。