What is the cause of myopia? Researchers in a country tracked more than 500 children aged 8-9 with normal vision. Five years later, they found that the only environmental factor related to myopia is the time children spend outdoors. Moreover, children's myopia is indeed related to the length of time they spend outdoors, whether they are exercising, having a picnic or just reading on the beach. 
The retina produces dopamine according to the circadian rhythm, so that the eyeball can switch from night vision to day vision. Under the dark indoor light during the day, the cycle of the retina will be disturbed and affect the development of the eyeball
 the researchers believe that, The more important cause of myopia may be whether the eyes are in bright light, which can protect the eyes.