Home » In Asia, more and more young people are short-sighted and need to run for cover

In Asia, more and more young people are short-sighted and need to run for cover

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In Asia, more and more young people are short-sighted and need to run for cover

In the early 1980s, the Taiwanese military realized it had a problem. Myopic recruits, who needed glasses to focus on distant objects, rapidly increased. “The fear was that in the worst case scenario [un attacco della Cina] their soldiers were at a disadvantage, ”says Ian Morgan, myopia expert at Australian National University in Canberra. A 1983 study conducted across the island confirmed that around 70 percent of Taiwanese college graduates needed glasses or contact lenses.

Today the figure has exceeded 80 percent. And so as not to hurt the Taiwanese generals, the problem is not just about the army. In fact, in recent decades, myopia has increased dramatically throughout East Asia: if in the sixties there were around 20-30 per cent of Chinese graduates and short-sighted female graduates, now they have reached their cousins ​​across the strait, with peaks higher than 80 percent in certain parts of the country.

Elsewhere, on the same continent, the situation is even worse. A study of male-only high school graduates in Seoul found that 97 percent were shortsighted. Hong Kong and Singapore follow with little distance. Despite having the worst figures, however, East Asia is not alone. For America and Europe reliable numbers are not yet available, but according to a 2015 summary, the European rate was between 20 and 40 percent, an order of magnitude higher than the percentage that insiders consider ” natural”.

Better not be … shortsighted
Myopia is usually an expensive and permanent inconvenience. The severe form, however, can result in loss of vision, says Annegret Dahlmann-Noor, chief ophthalmologist at London’s Moorfields eye hospital. A paper published in 2019 concluded that each worsening of a diopter was associated with a 67 percent increase in myopic maculopathy, an incurable disorder that causes blindness (diopter is the measure of the lens’s ability to focus).

In some parts of East Asia, 20 percent of young people have severe myopia, which is -6 diopters or worse. “The decades to come look problematic,” comments Kathryn Rose, director of the orthoptics department at the University of Technology in Sydney.

The phenomenon is beginning to attract the attention of the authorities. In 2018, Chinese President Xi Jinping made the control of childhood myopia a national priority. The restrictions imposed on the private gaming and video game sectors, which began in 2021, were partly motivated by concerns about the sight of the little ones, Morgan says. The governments of Taiwan and Singapore are also trying to take action. “Health authorities are starting to see myopia as a problem,” says Dahlmann-Noor.

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In most cases, the defect is caused by a malformation of the eyeball. A properly functioning eye directs light to the retina, the photosensitive surface at the bottom of the eyeball. In a myopic eye, however, the distortion is such as to direct the light near the retina. Myopic people see well up close, while distant objects are blurry. And the disorder is progressive, causing a worsening of vision during childhood and adolescence and then stabilizing in adulthood.

For decades, researchers thought it was mostly genetic in nature. Myopia is inherited and genomic studies have discovered several genetic variants responsible for the increased risk of developing it. Yet there were some clues that suggested something else. A study conducted on the Alaskan Inuit, and published in 1969, showed that myopia was virtually unknown in middle-aged or older people, while in children and teens it exceeded 50 percent. Such a change is all too rapid to be purely genetic and occurred concurrently with the adoption of a more sedentary and western lifestyle by the volunteers who underwent the study. The results, however, defied the dogma of the time, Morgan explains, and were ignored.

Controversial evidence
On the other hand, it is more difficult to liquidate the surge that occurred in East Asia with industrialization. The stereotype has it that myopia is a nerd disorder, and an avalanche of studies has confirmed a solid and reliable link with education. “The more educated you are, the higher grades you have and the more after-school and private lessons you have, the better your chances are [di essere miopi]”Says Morgan. And an interesting study of Orthodox Jewish children who lived in Israel in the 1990s confirmed the link with a long school time, showing that boys – undergoing intense religious training, in addition to normal courses of study – were more short-sighted than sisters.

Not finding an obvious and direct relationship between school or even religious education and the onset of myopia, different causes have been hypothesized. Among these, the well-known theory advanced over four hundred years ago by the German astronomer Kepler, who wore glasses, according to which myopia is associated with overwork involving near vision, such as reading and writing.

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While it’s still a widespread theory, Rose explains, the evidence supporting it is controversial at best.

According to the current dominant hypothesis, however, the main variable is the exposure to daylight. A study of boys and girls in California, published in 2007, found that time spent outdoors had a strong link with reducing the risk of myopia. Another study published the following year by Rose, Morgan and colleagues followed over four thousand Sydney boys and girls for three years to a similar conclusion. The type of activity – sports, walks, picnics – does not seem to affect. The important thing is to stay in natural light. In a comparison with Kepler’s hypothesis, the researchers found that spending time outdoors significantly reduced the risk of myopia in even the most studious children.

Diseases of well-being
The theory fits the data perfectly. He explains why myopia, like diabetes and heart disease, are also part of the so-called diseases of well-being – more common in rich countries – given that economic growth is accompanied by more education and therefore, for the very young, more time indoors. It also explains why the incidence is higher especially in East Asia, says Morgan, where the widespread diffusion of private and after-school lessons involves many more hours of study than in Western countries. In South Korea, for example, most boys and girls go tutoring in so-called schools hagwon and often has lessons until the evening.

The theory of exposure to daylight is also supported by animal studies – in which exposure can be precisely controlled – which invariably develop myopia in the presence of low light. The researchers also have an alleged mechanism. Exposure to bright light appears to stimulate the production of dopamine in the retina, a neurotransmitter which in turn helps regulate the growth rate of the eye. If it is scarce, the eye becomes too long to focus properly.

Clinical trials in humans also confirm this theory. One of the main, coordinated by Pei-Chang Wu of Taiwan’s Chang Gung University Medical School and published in 2020, reported the results of millions of Taiwanese schoolchildren who had attended primary school between 2001 and 2015. In the 2010 the government established the “Tian-Tian Outdoor 120” program, which encouraged schools to take pupils out for two hours a day. Since the program went into effect, myopia has declined slowly but steadily, from 49.4 percent in 2012 to 46.1 percent in 2015 and reversing an upward trend that had lasted for decades.

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Although it is not known exactly how much light is needed, Morgan is oriented around ten thousand lux, equal to about what is absorbed in the shade on a sunny day (direct light from the tropics can exceed one hundred thousand lux). Indoors, however, it rarely reaches over a thousand. The classrooms could be illuminated with ten thousand lux, Rose observes, but the amount of heat produced even with the LEDs would require special air conditioning and the glare would risk complicating reading.

Researchers are also attempting to slow the progression of myopia. One method devised involves low dosages of atropine, a poisonous chemical made from belladonna, the juice of which was once used to dilate the pupils and be more attractive. Another consists of special “ortho-k” contact lenses, designed to reshape the cornea (the clear front part of the eye that does the bulk of the job of directing light to the retina; the lens is used for regulation). While seeming effective, Rose fears the side effects of contact lenses in children because improper use risks irreversibly damaging the cornea.

Certain types of sophisticated eyewear are also useful. In 2020 the British Medical Journal published a Chinese trial on dims technology, peripheral positive defocus lenses: the lenses have a central zone that corrects vision and is surrounded by hundreds of smaller zones of different optical power. The aim is to allow clear vision through the central part and deliberately distorted vision through the smaller areas, because blurry vision is thought to slow the eye’s growth rate. Glasses with dims technology have roughly halved the progression of myopia.

Eye drops, lots of sunlight, and smart glasses could prevent or slow down myopia in future generations, but when it comes to maturity, the disorder becomes permanent. In some countries, therefore, a public health problem already exists. Who has very severe myopia and a high risk of complications, explains Rose, after the age of 40 can have dangerous changes in the eye, “in some cases incurable”.

(Translation by Stefania De Franco)

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