多做户外活动可预防儿童近视

近视眼在童年时期是可以纠正的

中文阅读：

英国《每日邮报》5月2日讯， 长期在户外玩耍的孩子最不容易得近视眼。

发表在美国眼科学会《眼科》杂志两项最新研究显示称日光对保护视力有着非常重要的作用。

虽然还不知道原因，但专家认为大脑中的化学成分多巴胺从中起了一定的作用。眼球中大量的多巴胺成分降低了患近视的危险。

近视眼在童年时期是可以纠正的，但是在成年会发展为眼疾，并有可能导致青光眼或视网膜脱落等疾病，丧失视力。

目前，在亚洲等富裕地区近视几乎已呈流行态势，在此背景下，有关近视方面的研究在近些年日渐增多。

如今美国患近视的人数也出现惊人增长，较1970年增加了65%。

虽然近视与遗传有关，但是研究人员正在评估外部环境的影响来解释为什么这种疾病在一些人群中呈现高发态势。

台湾高雄长庚医院的研究者吴裴昌选取了333名课间在操场活动的学生。这些学生以前大部分课间都在室内，现在每天都在户外活动80分钟左右。

而附近的另一所学校则没有强行让学生课间外出。两所学校的学生在研究伊始和一年终了分别接受了眼科检查。结果显示前一所学校学生患近视眼的比率要大大低于没有强行让学生课间外出的学校。

另外一项研究针对日光照射对眼睛发育的影响进行了分析，由中山大学的崔冬梅领衔。该项研究收集了235名患近视的丹麦学童的临床试验数据。

该项研究选择在丹麦进行，是因为丹麦日照时间随季节大幅波动，冬季仅为7小时，而夏季长达18小时。

参与实验的丹麦学童被分为7个组，每一组对应一年中不同的时间段。

实验收集了各组学童分别在对应的时间段的开始和结束时的眼球轴向长度以及视力测试数据。眼球轴向长度是一项重要的数据，眼球伸长表明近视加深。

在接触日光最少的一组学童，眼球轴向长度平均增长0.19毫米，而接触日光最多的一组学童，眼球长度仅增长0.12毫米。

“我们的研究结果表明，暴露于日光有助于防止儿童近视，家长应鼓励儿童每天多在户外活动。” 执行该项研究的崔冬梅教授建议。

“因为天气或其他原因无法在户外活动，也可以在室内使用日光光谱的照明灯作为替代，以尽量减少近视。”(编译： 吴瑾 王志永)

原文阅读：

Children who spend more time playing outside are less likely to suffer from short-sightedness。

Two new studies have added to the body of evidence that daylight plays an important role in preventing the condition。

It is not known why daylight is important but some experts believe levels of the brain chemical dopamine play a role. High levels of dopamine in the eyeball have been associated with a lower risk of short-sightedness。

Short-sightedness, or myopia, is an eye condition that causes a person to see things clearly close-up but struggle to see things when they are far away。

In childhood it is correctable, but it is also linked to the development of severe forms of the eye disorder in adulthood, which increases the risks for potentially blinding diseases such as glaucoma and retinal detachment。

Research on short-sightedness is intensifying as the condition nears epidemic status in Asia and other regions, primarily in developed countries。

Shockingly, it has increased by more than 65 per cent since 1970 in the U.S。。

Although it often inherited, researchers are now assessing environmental factors to help explain why rates are rising so rapidly in some populations。

The Taiwanese study observed 333 students who spent their break between lessons in the playground. These children, many of whom had formerly spent recess indoors, now spent a total of 80 minutes per day outdoors。

A nearby school acted as the control group because children were not forced to spend their break outdoors。

Students at both schools received eye examinations at the study outset and one year later。

The results showed that significantly fewer children became short-sighted or shifted toward short-sightedness in the school that required outdoor breaks, compared with the control school。

The researchers recommended that primary schools should add frequent breaks and other outdoor activities to their daily schedules to help protect children's eye development and vision。

‘Because children spend a lot of time in school, a school-based intervention [such as an outdoors break] is a direct and practical way to tackle the increasing prevalence of myopia,’ said the leader of the study, Pei-Chang Wu, of Kaohsiung Chang Gung Memorial Hospital in Kaohsiung, Taiwan。

A separate study on the impact of daylight exposure on eye development analysed data collected in a 2005 clinical trial that included 235 Danish school children with short-sightedness。

Participants were divided into seven groups, each of which represented a different time of year。

Because daylight hours fluctuate dramatically with the seasons in Denmark - from seven hours in winter to nearly 18 in summer - access to daylight was distinct for each group。

Axial eye length – the distance from the front to the back of the eye – and vision were tested in each group of children at the beginning and end of their seasonal interval。

Axial length is an important measurement because elongation of the eye shows that myopia is worsening。

In the children with access to the fewest hours of daylight, eye growth averaged 0.19 mm; in those with access to the most daylight, eye growth was just 0.12 mm。

‘Our results indicate that exposure to daylight helps protect children from myopia,’ said the leader of the study, Dongmei Cui of Sun Yat-sen University, China。

‘Parents should encourage [children] to spend time outdoors daily。

‘When that's impractical due to weather or other factors, use of daylight-spectrum indoor lights should be considered as a way to minimize myopia.’

Both studies were published in Ophthalmology, the journal of the American Academy of Ophthalmology。