An interesting article caught my eye. It turns out that according to statistics, 90% of Chinese teenagers suffer from myopia, with the world average at 22%. Moreover, if you consider other regions, only 1.2% of inhabitants of Nepalese villages, 4% of South African children, and 12% of American teenagers suffer from myopia. Imagine, according to the data in the article, in Seoul 96.5% of 19-year-olds are myopic. That is, almost everyone. The question is why myopia among teenagers in China and Korea is so prevalent.
Previously, this was attributed to genetics, but just 60 years ago, the percentage of myopic teenagers in China was only 10-20%. Clearly, it’s not just genetics.
At first, they blamed reading. It was suggested that focusing on letters gradually changes vision. But with the advent of computers being ubiquitous, enough data has accumulated that doesn’t quite align with the conclusions about reading, and ultimately, this hypothesis has become much fainter.
It turned out that a lack of natural light significantly affects this condition. Scientists have discovered that children who spend more time outdoors are less likely to develop myopia.
Of course, correlation does not imply causation, and science needs a mechanism. There are several hypotheses that attempt to explain how this happens.
The most compelling seems to be the hypothesis called the light and dopamine hypothesis, which suggests that light stimulates the release of dopamine in the retina, thereby maintaining the correct shape of the retina. Research on chickens seems to have confirmed this idea. Retinal dopamine is produced depending on the circadian cycle, instructing the eye to switch from night vision, based on rod cells, to daylight vision, based on cone cells. Thus, spending less time outdoors and more time indoors (under the influence of artificial light) disrupts this cycle and normal eye function.
Hi, I'm Rauf Aliev. 