如果說(shuō)年輕時(shí)近視的我們，老了之后會(huì)遠(yuǎn)視，那么，是不是會(huì)有那么一段時(shí)間，我們的視力能好到看清視力表最下面那一排“鬼畫符”呢？

答案是：不一定。

事實(shí)是這樣的：

Babies are actually farsighted, and as they grow older their eyes grow too until they reach a point of "perfect" eyesight, called emmetropia.

剛出生的嬰兒都是遠(yuǎn)視眼，但隨著年齡增長(zhǎng)，眼睛也會(huì)發(fā)育，直到“視力正?！?，學(xué)術(shù)上叫做“屈光正?！保╡mmetropia）。

出生的時(shí)候，嬰兒都一樣，都是遠(yuǎn)視眼。等慢慢長(zhǎng)大，兒童的視力就正常了。但很多人青春期長(zhǎng)著長(zhǎng)著就過(guò)了那個(gè)點(diǎn)，變成了近視。

It isn't entirely worked out what cues the eye that it is time to stop growing, but we know that in many kids the eye continues to grow past emmetropia and they become nearsighted.

其實(shí)直到現(xiàn)在（科學(xué)家）也還沒(méi)有完全弄清楚是什么因素“告訴”眼睛該停止發(fā)育了。但我們知道，很多孩子的眼睛在視力正常后繼續(xù)發(fā)育，結(jié)果變成了近視。

Basically, when the eye grows too long the light inside the eye comes to a focus in front of the retina rather than at the retina, causing blurry vision, so we must wear glasses to change the optics and focus the light onto the retina again.

是這樣的，如果眼睛的前后距離太長(zhǎng)，眼睛里的光線就會(huì)聚焦在視網(wǎng)膜前面而不是視網(wǎng)膜上，從而造成了模糊的視覺(jué)，因此，我們必須戴上眼鏡來(lái)改變光線的路徑，使它再次聚焦到視網(wǎng)膜上。

When we age, we suffer a different process. Our tissues become stiffer and the lens doesn't adjust as easily so we start to lose near vision as well.

隨著年齡增長(zhǎng)，我們會(huì)經(jīng)歷一個(gè)不同的過(guò)程。我們的眼部組織會(huì)變得僵硬，晶狀體的活動(dòng)性也變差，漸漸地，我們就連近的東西也看不清了。

等到老了，以為遠(yuǎn)視可以把它拉回來(lái)，卻發(fā)現(xiàn)晶狀體已經(jīng)失去了彈性，近視遠(yuǎn)視并存，需要兩幅眼鏡了。

Many older folks must wear bifocals which have two different lenses- one to correct for the problems with near vision and one to correct for problems with far vision.

許多老年人必須佩戴有兩種不同鏡片的雙焦眼鏡，一種用于矯正近視問(wèn)題，另一種用于矯正遠(yuǎn)視問(wèn)題。

環(huán)顧四周，想想看，你身邊戴眼鏡的人占多大比重？

事實(shí)上，中國(guó)青年的近視問(wèn)題早就見(jiàn)諸國(guó)際媒體的報(bào)端。

今年四月份，China Daily就曾報(bào)道過(guò)學(xué)生的近視問(wèn)題：

More than half the young children and teenagers in China are nearsighted, according to a survey by top government agencies, which called for intensified efforts to prevent and control the condition.

相關(guān)部門的一項(xiàng)研究顯示，中國(guó)有一半以上的兒童和青少年是近視眼，該研究呼吁加大預(yù)防和控制近視的力度。

The survey, which was conducted last year, found that eight of 10 senior middle school students were nearsighted, compared with 71.6 percent in junior middle school, 36 percent in primary school and 14 percent of 6-year-olds in kindergarten. Overall, 53.6 percent were nearsighted.

去年進(jìn)行的這項(xiàng)研究發(fā)現(xiàn)，10名高中生中有8人近視，而初中生近視率為71.6%，小學(xué)生近視率為36%，幼兒園6歲兒童近視率為14%?？偟膩?lái)看，也有53.6%的人患有近視。

新華社的同期報(bào)道也顯示，高中生近視人群中高度近視的人數(shù)也有顯著增加。

The prevalence of a high degree of myopia also became alarming as the percentage of senior students in high school, who wear glasses stronger than six diopters, has mounted to 21.9 percent.

高度近視的患病率也令人擔(dān)憂——高中生中戴著600度以上近視眼鏡的比例已經(jīng)上升到了21.9%

權(quán)威醫(yī)學(xué)雜志《柳葉刀》在2018年的一項(xiàng)針對(duì)中國(guó)青年群體的研究中發(fā)現(xiàn)：

Up to 80 percent of the country’s young adults suffer from nearsightedness, according to a report in the medical journal Lancet. In contrast, the overall rate of myopia in the UK is about 20-30 percent.

醫(yī)學(xué)雜志《柳葉刀》的一項(xiàng)報(bào)告顯示，（中國(guó)）80%的年輕人患有近視。相比之下，英國(guó)的近視率大約為20%-30%。

早在2015年，美國(guó)國(guó)家公共電臺(tái)引述新華社報(bào)道的數(shù)字稱當(dāng)時(shí)就有86%的高中生患有近視了：

If you walk the streets of China today, you'll quickly notice that most young people wear glasses. In Shanghai, for instance, 86 percent of high school students suffer from myopia, or nearsightedness, according to Xinhua News Agency.

走在如今的中國(guó)街頭，你會(huì)很快注意到大多數(shù)年輕人都戴著眼鏡。以上海為例，據(jù)新華社報(bào)道，86%的高中生患有近視。

類似的數(shù)字還被《每日電訊報(bào)》、半島電視臺(tái)和石英網(wǎng)等媒體報(bào)道過(guò)。

之后，2017年《南華早報(bào)》的報(bào)道引述了《柳葉刀》的一項(xiàng)研究顯示：青少年大范圍近視不僅僅是中國(guó)一個(gè)國(guó)家的問(wèn)題，是整個(gè)東亞地區(qū)的問(wèn)題。

The growing prevalence of myopia is not only a Chinese problem, but it is an especially East Asian one. According to a study published in The Lancet medical journal in 2012, by Ian Morgan, of the Australian National University, South Korea leads the pack, with 96 percent of young adults (below the age 20) having myopia; and the rate for Seoul is even higher. In Singapore, the figure is 82 percent.

近視患病率的不斷上升不僅是中國(guó)一個(gè)國(guó)家的問(wèn)題，而是困擾整個(gè)東亞的問(wèn)題。澳大利亞國(guó)立大學(xué)的伊恩·摩根2012年在《柳葉刀》上發(fā)表的一項(xiàng)研究顯示，韓國(guó)的近視率高居榜首，96%的年輕人（20歲以下）患有近視，首爾的近視率甚至更高。新加坡的這個(gè)數(shù)字是82%。

ZME Science的標(biāo)題更是嚇人：To say that Asia is having an eye problem is an understatement.說(shuō)是“亞洲近視”都不為過(guò)。

近視的原因到底是什么？

China Daily的報(bào)道總結(jié)了近視的幾大原因：

Several factors are associated with the high rate of nearsightedness in China's children and teenagers, including lack of outdoor physical activity, lack of adequate sleep due to heavy extracurricular work and excessive use of electronics products.

有若干個(gè)因素與中國(guó)兒童和青少年近視率高有關(guān)，包括缺乏戶外體育活動(dòng)、課余作業(yè)繁重導(dǎo)致睡眠不足，以及過(guò)度使用電子產(chǎn)品。

久坐不出門、睡眠少、看手機(jī)多，這說(shuō)的不就是我嗎？

書本拿太近，電子產(chǎn)品用太多已經(jīng)是老生常談了。但發(fā)表在權(quán)威雜志《眼科》上的一項(xiàng)研究顯示戶外活動(dòng)的確是一個(gè)重要因素：

Biologists compared Singaporeans living in Singapore to those living in Australia. They found that 29 percent of the Singaporean students had myopia compared with just 3 percent in Sydney. The main correlation was once again, time spent outside.

生物學(xué)家把居住在新加坡的新加坡人與居住在澳大利亞的新加坡人作了比較。他們發(fā)現(xiàn)29%的新加坡學(xué)生患有近視，而在悉尼的那一組中就只有3%。主要的關(guān)聯(lián)再次出現(xiàn)在花在戶外的時(shí)間上。

“The big difference was the Chinese children in Australia were outdoors a lot more than their matched peers in Singapore,” says Ian Morgan, a retired biologist at Australian National University, who coauthored the 2008 study. “This was the only thing that fit with the huge difference in prevalence.”

澳大利亞國(guó)立大學(xué)退休生物學(xué)家伊恩·摩根表示：“兩組之間最大的不同在于，與新加坡的同齡人相比，澳大利亞的華裔在戶外活動(dòng)的時(shí)間多得多。這也是唯一能解釋近視率巨大差異的因素。”

最后來(lái)回顧一下與視力相關(guān)的單詞吧！

近視可以叫nearsightedness,也可以叫shortsightedness,醫(yī)學(xué)上叫做myopia.

同理，遠(yuǎn)視就是farsightedness，或者longsightedness,前一個(gè)偏美式，后一個(gè)則偏英式，學(xué)術(shù)上的遠(yuǎn)視叫做hyperopia.

Notes

myopia /ma??o?pi?/ n.近視

hyperopia /ha?p??o?pi?/ n.遠(yuǎn)視

bifocals /ba??fo?klz/ n.雙光眼鏡（上半片為看遠(yuǎn)，下半片為看近）

retina /?ret?n?/ n.視網(wǎng)膜

lens /lenz/ n.（眼球的）晶狀體

prevalence /?prev?l?ns/ n.流行；盛行

understatement /??nd?ste?tm?nt/ n.保守說(shuō)法；低調(diào)說(shuō)法；輕描淡寫

編輯：唐曉敏

實(shí)習(xí)生：崔鶯馨

來(lái)源：The Lancet《南華早報(bào)》ZMEScience  Ophthalmology NPR等