Did you know that according to statistics up to 90% of Chinese urban adolescents are nearsighted by the time they finish school—while the global average was about 23% in 2000 and rose to approximately 34% by 2020? In other regions, only 1.2% of Nepalese village residents, 4% of South African children, and 12% of American teenagers are nearsighted. Imagine this, according to data from the article, in Seoul 96.5% of 19-year-old boys are nearsighted (though, this figure only covers conscripts from the capital; across all of Korea, the number among 19-year-olds is more modest—about 55–60%). But even so—almost everyone. The best explanation available is the “light and dopamine” hypothesis, which posits that light stimulates the release of dopamine in the retina, inhibiting excessive elongation of the eyeball. Retinal dopamine is produced according to the diurnal cycle, signaling the eye to switch from night vision, based on rod cells, to daytime vision, based on cone cells. Let there be light! The image shows a test for nearsightedness.
Hi, I'm Rauf Aliev. 