“For many years, the scientific consensus held that myopia was largely down to genes….
“Researchers have consistently documented a strong association between measures of education and the prevalence of myopia…
“Attractive though the idea was, it did not hold up. In the early 2000s, when researchers started to look at specific behaviours, such as books read per week or hours spent reading or using a computer, none seemed to be a major contributor to myopia risk.
“”The team examined how the children spent their days, and “sort of as an afterthought at the time, we asked about sports and outdoorsy stuff”, says Mutti.
“It was a good thing they did. After five years, one in five of the children had developed myopia, and the only environmental factor that was strongly associated with risk was time spent outdoors.
“Retinal dopamine is normally produced on a diurnal cycle — ramping up during the day — and it tells the eye to switch from rod-based, nighttime vision to cone-based, daytime vision. Researchers now suspect that under dim (typically indoor) lighting, the cycle is disrupted, with consequences for eye growth. ”