What blurred the eyes of 450 million Chinese people

Abstract: myopia, as an epidemic, has only appeared on a large scale in China in recent decades. In 2014, the economist reported that in the 1970s, less than one-third of Chinese teenagers aged 16-18 were myopia. But today, nearly four fifths of teenagers suffer from myopia.

when you see this article, you might as well look around you and observe your colleagues, your classmates and strangers around you. You will find that most people wear glasses, and you don’t have to ask. Most of them are myopic.

myopia, as an epidemic, has only appeared on a large scale in China in recent decades. In 2014, the economist reported that in the 1970s, less than one-third of Chinese teenagers aged 16-18 were myopia. But today, nearly four fifths of teenagers suffer from myopia.

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the national visual health report released by Peking University in 2016 also shows that China’s myopic population over the age of 5 has reached 450 million and will exceed 700 million in 2020. China has become a truly invisible country.

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have been suffering from myopia in East Asia except for Chinese mainland. In Hong Kong, Taiwan, Japan, South Korea and Singapore, nine out of ten students who finish high school are myopic, of which 10% – 20% are highly myopic.

in Seoul, South Korea, the myopia rate of 19-year-old boys has even reached an incredible 96.5%. Considering the cultural similarity in East Asia, the trouble they encounter is of course the trouble of Chinese mainland.

so why are there more and more East Asians, especially Chinese, with myopia? Are Chinese people naturally prone to myopia? Or are the Chinese all learning maniacs who grow up gnawing at books?

Chinese myopia frenzy

we have to answer a question first, what is myopia. In short, your eyes contract or relax the muscles that control the lens in order to see a nearby or distant object, so that the shape of the object can be projected onto the retina. Myopia is due to the lengthening of the eyeball. After the light comes in, it does not focus on the retina, but on a little bit in front.

myopia is certainly not as terrible as cancer or heart disease, but the large-scale prevalence of myopia brings more than the inconvenience of wearing glasses. In particular, high myopia may not be a big deal when young, but it is easy to induce cataract and glaucoma after middle age.

for many years, scientists have blamed myopia on genes. In the 1960s, research was done in this direction, For example, a study found that identical twins (genetically identical) are more likely to get myopia than fraternal twins, which shows that the effect of DNA on myopia should not be underestimated. Scientists have found more than 100 regions in the genome related to myopia.

If the parents are myopic, the child is indeed more likely to be myopic. In 2012, a joint study by Sun Yat sen University and Australian National University showed that among 15-year-old teenagers in Guangzhou, China, if a pair of parents are myopic, the child’s myopia rate will be as high as 83.3%; If one of the parents has myopia, the myopia rate of the child is a little worse, 88.9%; If parents have good eyesight, the child’s myopia rate will drop to 68.2%.

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but genes can’t explain the surge in the number of men and women with glasses in China. Genes can’t explain why the myopia rate of 15-year-old teenagers in Guangzhou, China is 78.4%, but only 19.8% of their parents have bad eyes. Genes cannot explain why the myopia rate in urban areas is higher than that in rural areas, especially among high school students.

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are the same, Genes can’t explain why 22.9% of 10-year-old students in Shaanxi (ranking 14 in per capita GDP) suffered from myopia in 2012, but the myopia rate of equivalent students in Gansu (ranking 30 in per capita GDP) next door was only 12.7%.

Heredity does play a role, but it is impossible to set off this wave of myopia only by itself. Contemporary myopia is not only a genetic problem, but also a social problem.

don’t blame books and TV

in order to catch the culprit of large-scale damage to vision, scientists try to blame myopia on “nearwork”. After all, compared with European and American students, Chinese students have to spend more time on books.

according to a 2014 OECD report, 15-year-old students in Shanghai spend 14 hours a week doing their homework, while American students spend only 6 hours a week, and British students spend less, only 5 hours.

the myopia rate of Chinese students is rising, accompanied by the infinite extension of their learning time. In addition to learning to read endlessly, watching TV, playing with mobile phones and playing with computers have also become the object of parents’ blame. However, no matter how hard scientists try to associate “close work” with myopia, the causal relationship between them is not so strong.

in 2007, Ohio State University released a research result. They followed the eyesight of 514 American students in grade 3. Five years later, 111 students were found to have myopia. Myopia is related to parents’ heredity, sports and outdoor sports, but it has nothing to do with the length of reading a week.

later, members of the research team recalled to the journal Nature, “we think this is really a strange result”, “but when we do analysis, such results always appear”.

if you think Americans are not able to represent Asians, there are also studies in Asia. In 2006, the National University of Singapore conducted a three-year study on a group of 7-9-year-old Singaporean students and found that reading a few books a week could not be used to predict whether children would become myopia in the next few years.

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then the researchers analyzed the length of time spent reading and playing computer every day, and found that myopic students may just prefer reading, rather than reading leads to myopia.

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constantly have new evidence challenging the traditional cognition of “myopia caused by seeing too close”. twoIn 2015, the same Ohio State University released a study that overturned the tradition. The 20-year study of 4512 American children shows that reading, watching TV or playing computer for a long time and sitting too close are not the direct causes of myopia.

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although the research is aimed at American children, the research spans white, black, Aboriginal, Latino and Asian children in the United States. The reasons are similar.

children are too short of outdoor sports.

close reading, watching TV or playing games should not be the pot for myopia. Who will carry the pot? Scientists have not yet fully understood the real cause of myopia, but they are reaching a consensus that the less outdoor exercise, the more likely they are to get myopia.

in 2008, Kathryn rose of the University of Sydney, Australia, compared 6-7-year-old Chinese children in Sydney, Australia with 6-7-year-old Chinese children in Singapore. As a result, her team found that the myopia rate of Chinese children in Sydney was only 3.3%, but the myopia rate of Chinese children in Singapore was as high as 29.1%.

even more amazing, The parents of children in both places have the same myopia rate (Sydney 68%vs Singapore 71%), and Chinese children in Sydney read more books every week and often look at objects at close range. Obviously, they are descendants of Chinese people. Why do children in the two places have different eyesight? The most important factor found by Ross team is the length of outdoor activities: Chinese children in Sydney spend 13.75 hours on outdoor activities every week, compared with 13.75 hours , Chinese children in Singapore spend only 3.05 hours a week outdoors.

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Ross team guessed that children who often participate in outdoor activities receive more light intensity. Light can stimulate the release of dopamine in the retina. This neurotransmitter can protect the eyeball from becoming too long, so as to prevent myopia. On sunny days, the outdoor light intensity may range from 20000 to 100000 lux (lighting units), while the indoor light intensity may be less than 500 lux. China’s Ministry of education requires that the average illumination on the desk of primary and secondary school classrooms should not be less than 300 lux.

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some scientists have experimented with chickens, sloths and monkeys, and the results have supported the above hypothesis. However, some scientists have criticized The “light dopamine” mechanism is too simple and rough. Outdoor exercise can reduce myopia for a variety of complex reasons. Andy Fischer of Ohio State University pointed out that the outdoor vision is better, and the eyes can be in a relatively relaxed state, which may block the poor growth of the eyes.

anyway, even if the underlying mechanism is not clear for the time being, it has gradually become a consensus that outdoor sports can help protect eyesight. In 2012, a study conducted in southern Taiwan showed that all school students aged 7-11 were driven outdoors in only 80 minutes after class. A year later, the myopia rate of these students was 50% lower than that of the school next door. In 2013, another study conducted in Guangzhou for two years showed that giving children 45 minutes of outdoor time every day could finally reduce the incidence of myopia by 25%.

because most studies only found the leading role of outdoor sports, it means that no matter how many sports activities or eye exercises are carried out indoors, it is useless. In fact, most authoritative ophthalmology societies and ophthalmologists in the world believe that various forms of eye exercises do not help to improve vision.

China is facing the most serious myopia problem in the world, and it is urgent to update public health policies. Unfortunately, until November 2016, the national health and Family Planning Commission, the Ministry of education and the General Administration of sports still jointly issued a document, requiring that physical activities should not be less than 1 hour a day. At the same time, it stressed that eye exercises twice a day should be included in the curriculum, which is called strengthening myopia prevention and control.

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do not need to “protect vision for the revolution” now, but Chinese children still have to repeat meaningless actions in the classroom day after day, naively believing that they have protected their eyes.