Interesting article. It turns out that according to statistics, 90% of Chinese teenagers suffer from myopia, with the global average being 22%. Meanwhile, only 1.2% of residents in Nepalese villages, 4% of South African children, and 12% of American teenagers suffer from myopia. The question is why.
Previously, this was attributed to genetics, but just 60 years ago, the percentage of myopic teenagers in China itself was between 10-20%. Clearly, it’s not just genetics.
Imagine, according to the data from the article, 96.5% of 19-year-olds in Seoul are myopic. Basically, almost everyone.
Initially, they blamed reading. Supposedly focusing on the letters gradually alters vision. But with the advent of computers everywhere, enough data has been gathered that didn’t quite agree with the conclusions about reading, and eventually, this hypothesis faded significantly.
It turned out that a lack of natural light significantly influences the condition. Scientists discovered that children who spend more time outdoors are less likely to become myopic.
Of course, correlation does not imply causation, and science needs a mechanism. There are several hypotheses that try to explain how this happens. The most promising seems to be the light and dopamine hypothesis, which states that light stimulates the release of dopamine in the retina, thereby maintaining the correct shape of the retina. Research in chickens seems to have confirmed this idea. Retinal dopamine is produced depending on the diurnal cycle, signaling the eye to switch from nocturnal vision, based on rod cells, to daytime vision, based on cone cells. Thus, spending less time outdoors and more time indoors (under artificial light) disrupts this cycle and the normal functioning of the eye.
Hi, I'm Rauf Aliev. 