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The number of children who need glasses to see far away objects -- a condition known as myopia -- is increasing and current projections suggest that by 2050, 50 percent of the world's population will be affected.
近视需要配戴眼镜方能看清远处物体，小儿近视的数量正在上升，根据目前的预测，到2050年，世界50%人口都将受到近视困扰。
In the 1970s, 25 percent of Americans had myopia; but just three decades later prevalence rose to 42 percent.
20世纪70年代，美国有25%的人口近视；而只过了30年，近视率就升到了42%。
Although genetics is responsible for some cases of myopia, scientists now believe that environment also plays a major role.
虽然在某些案例中，基因是导致近视的原因，但今天的科学家认为环境同样起着重大影响。
Now researchers are starting to untangle the reasons for the skyrocketing rates and devise ways of slowing down and reversing a child's declining vision -- which is important for their overall quality of life and their risk for developing vision loss later in life.
现在，研究人员正着手厘清近视率激增的原因，设计治疗方案以减缓甚至反转儿童视力衰退的进程--视力对于孩子的整体生活质量至关重要，与日后会否发展出其他视力损失也有深刻关系。
"Kids are becoming nearsighted at rates that are faster than we've ever seen before," says Nick Onken, an optometrist at the University of Alabama, Birmingham. "It's faster than even genetics alone can account for."
“儿童近视的速率比从前任何时候观察到的都更快，”阿拉巴马大学伯明翰分校的验光师尼克·昂肯说，“远远超过了单靠基因能产生的近视速率。”
"We've known for decades that the more nearsighted the person is," says Onken, "the higher the likelihood they are for losing vision when they're older, due to conditions like retinal detachment, glaucoma, macular degeneration and cataracts."
昂肯说：“几十年来我们一直知道，人的近视程度越深，在年龄增长后失去视力的可能性就更大，这可能是视网膜剥离、青光眼、黄斑变性及白内障等多种情况引起的。”
Myopia often starts during childhood, due to a mismatch between how fast the eye is growing and where light is focusing on the retina.
近视常常发生于童年期，是眼睛发育速度与光聚集在视网膜的位置不匹配引起的。
"The condition of myopia or nearsightedness is caused by the fact that the eye is too long," says Carolyn Lederman, an ophthalmologist based in Purchase, New York.
“近视的成因是眼球过长。”纽约帕切斯的眼科专家卡罗琳·莱德曼说。
When the entire eyeball grows longer than it should, this creates a situation where the focusing components of the eye -- the cornea and the lens -- target light just in front of the retina, rather than on the retina, which causes far-away objects to appear blurry.
如果眼球整体发育超过了应有长度，就会导致眼睛负责聚焦的结构--角膜与晶状体--使光线落在视网膜前，而非视网膜上，因此导致远处物体看起来模糊不清。
As it turns out, the age at which a child first becomes myopic is often predictive of how bad their vision will end up.
研究结果显示，儿童首次发生近视的年龄通常有助于预测其视力发展的最差情况。
"The biggest predictor of how nearsighted you're going to be, is when you become nearsighted," says Jeffrey Walline, an optometrist and associate dean of research at The Ohio State University.
“关于将来近视程度的最大预测项是开始近视的年龄。”俄亥俄州立大学研究院副院长、验光师杰弗里·沃林说。
As Walline explains, the younger a child is when they first become nearsighted, the worse it will end up as, due to the length of time that the eyeball spends growing longer than it should.
他解释道，孩子首次出现近视的年龄越早，最后结果就会越糟，病情发展取决于眼球超出其应有长度后又发育了多久。
For most children, their vision will stabilize during their late teenage years, although for a minority of individuals, this process will last until their mid-20s.
大部分孩子的视力会在青少年晚期固定下来，不过极小部分人的视力发育还会延续到20多岁。
In addition to needing corrective glasses or contacts to see properly, people with myopia are also at a much higher risk for developing vision problems later in life.
近视人群需要佩戴框架或隐形矫正眼镜，他们还有更高的风险在以后的人生中出现视力问题。
As Ann Shue, an ophthalmologist at Stanford University, explains, when the eye is just a little bit bigger than it should be, this stretches it out, similar to pizza dough, which can affect the very delicate nerves and blood vessels of the retina that are attached to the back of the eye.
斯坦福大学眼科专家安·舒解释说，只要眼睛比标准尺寸大一点点，它就会向外拉伸，像比萨面团似的，这会影响到位于眼球后部的视网膜那极度精密的神经与血管。
"As we get older, that can pull on the retina," causing issues such as glaucoma, retinal detachment or macular eye degeneration, Shue says.
舒说，“随着年龄增长，视网膜会受到牵拉”，继而产生青光眼、视网膜脱落或黄斑变性等眼部问题。
