In some classrooms in China, a kind of railing attached to the desk separates the child from the table and keeps his or her eyes from the book at a safe distance. In other schools, children wear a hat with a ball that dances on the brim: if the ball falls off, it means that the children have bent their heads too much and have gotten too close to their notebook. All these picturesque initiatives are designed to combat the rise of myopia, which is particularly high in some Asian countries and is expanding throughout the world. Experts warn that, sponsored by the abuse of screens and the decrease in outdoor activity, this optical defect does not stop growing and predict that by 2050 half of the world’s population will be short-sighted.
This condition is a common disorder of visual focus due to an enlargement of the eye. “It is an eye that grows more than it should for its age. The axial length, which is the distance between the cornea and the retina, increases and the focus point is in front of the retina. [y no sobre ella]“The axial length of a healthy eye is usually about 23 millimetres, but in a myopic eye it can reach 30 or 35 millimetres. In practice, this deformation of the eye causes the light rays to refract incorrectly and the focus point to deviate, which results in blurred vision of distant objects.
There are different degrees of myopia, but the experts consulted point out that from three diopters onwards “it is already difficult to lead a normal life” without correction; with glasses, for example. And the more affected the condition is – such as high myopia, when a person has more than six diopters – the greater the risk of developing pathological ocular changes that can cause irreversible vision loss, such as cataracts, glaucoma, retinal detachment and myopic macular degeneration. In 2010, it was estimated that uncorrected refractive error was the most common cause of distance vision impairment and the second most common cause of blindness worldwide.
“It is already a public health problem,” warns Miguel Ángel Sánchez Tena, a researcher at the Department of Optometry and Vision at the Complutense University of Madrid. In countries such as China, South Korea, Japan and Singapore, around 80% of children who finish secondary school suffer from this visual defect and of these, between 10% and 20% are very myopic, which means they have a higher risk of developing a potentially blinding pathological condition.
But the rise of this optical defect is not limited to Southeast Asia. The planet sees increasingly blurry. scientific review In 2016, the World Bank found that 1.4 billion people were nearsighted at the beginning of the 21st century and predicted that by 2050, that number would rise to 4.758 billion. That is, almost half of the world’s population, although there are differences by region: by mid-century, the prevalence of myopia in East Africa will not reach 23%, while in high-income countries in Asia and the Pacific, two out of three people will suffer from this condition.
“We are noticing the increase in cases in the pediatric population consultations: there are more people with myopia and it progresses more quickly,” says Luis Fernández-Vega Cueto-Felgueroso, an ophthalmologist at the Cornea and Lens Unit of the Fernández-Vega Institute. In Spain, a recent research Led by Sánchez Tena and Cristina Álvarez Peregrino, the study showed that the prevalence of myopia in children aged five to seven is 19%, but will reach 30% by 2030.
Multifactorial origin
According to Sánchez Tena, this phenomenon is multifactorial. Genetics play a role – although it is not clear which genes are involved – as do environmental factors and also race: Asians have a higher risk than Caucasians or black people. “There is a genetic component: children of parents with myopia will have a higher risk of developing it. But close work or digital devices also play a role,” summarises the Complutense scientist. Age is also another risk indicator: children who already have 1.25 diopters between the ages of six and seven are more likely to progress more quickly.
Australian researchers who estimated the prevalence for 2050 agree that the projected increases are due, above all, to environmental factors related to upbringing, “mainly, lifestyle changes resulting from a combination of less time outdoors and an increase in nearby work activities.” Regarding genetic factors, they say, they may play a role, but this variable alone could not explain the rapid expansion of myopia in the world.
Among other environmental factors, scientists also point out that “so-called high-pressure education systems, especially at very early ages in countries such as Singapore, Korea, Taiwan and China, may be a causal lifestyle change, as may the excessive use of nearby electronic devices.” Other causes are light levels, which may be related to the time children spend outdoors, or even diet. “The light from screens does not damage the eye, but overuse of screens does promote eye fatigue.” [estos problemas ópticos]”If we used screens in a good way, there would be no problem. But children are now abusing them more,” says Fernández-Vega Cueto-Felgueroso.
Alarcón also highlights the abuse of screens and less exposure to the sun. “When we look closely, we make an extra effort to focus and that makes us lose focus.” [el ojo] “There is no study that shows that one factor has more influence than another, but there are studies in China that show that giving classes outdoors, to expose children to ambient light, helps to slow the progression of myopia,” he points out. The explanationaccording to studies with animal models, is that, due to the brighter light outside, the release of retinal dopamine increases, which helps to decrease axial length.
Delay progression
Myopia is usually detected in childhood and can increase until adulthood, around the age of 22. Ophthalmologists point out that it is increasingly diagnosed at earlier ages, but it is also in these phases of life when work can be done best because the eye is still forming and there is more plasticity. There are several approaches to slowing the progression, explains Alarcón: “We have special lenses that create a blur in the peripheral area of the retina and that activates receptors that prevent it from growing as much. And we also have contact lenses and glasses that tighten the cornea to shorten the eye.” Another option, he points out, is atropine drops: “These drops, at very low concentrations, slow the progression because it is believed that they act on these areas of the retina. The problem is that they are not marketed and right now they are used as a magistral formula because there is no way for us to find a laboratory that markets these highly diluted drops.”
None of these are curative, but “if you manage to slow down the progression, it is already very important,” says Sánchez-Tena: “A myopic eye does not return to normal. But childhood is a window of opportunity and although you do not stop growth completely, the more you delay it, the better.” Glasses, contact lenses or corrective surgery eliminate this blurred vision, but they do not stop the eye from growing.
And beyond the overall vision problem, experts ar
e particularly concerned about the expansion of cases of more severe myopia, which hide a greater risk of developing complex optical pathologies. “Every diopter matters. If it were just a matter of putting on glasses and seeing well, that’s it. But the problem is what happens at the end of the eye. Your eye will be myopic for life, even if you don’t have to use correction,” says Sánchez Tena. For example, highly myopic people are 20 times more likely to suffer a retinal detachment throughout their life than an emmetropic individual (with normal vision). “The retina that lines the inside of the eye becomes so tense that holes can appear and there is a greater risk of retinal detachment,” explains the ophthalmologist from Vall d’Hebron.
With this situation on the table, experts urge to take measures. At a preventive level, says Alarcón, “the only effective thing is to do more outdoor activities while reducing close-up tasks.” The ophthalmologist from the Fernández-Vega Institute appeals to “the 20-20-20 rule: every 20 minutes, look 20 feet away for 20 seconds, which is about six meters. We must try to get young people to control the use of close-up devices and to have good lighting, not to be in the dark and to take breaks looking into the distance.”
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