alt Hacker NewsMain factor is genetics.
I was gaming on a blurry CRT and reading on a dim light while hardly ever going outside during my teens and I only have light myopia on one eye.
I don't know if it has ever been studied, but I suspect eye socket morphology from my own family anecdata.
large eyes + small socket = squashed eyes.
It could be different genetic factors for different populations too.
I agree that genetics can protect you from developing myopia. For people who are genetically susceptible, outdoor exposure is critically important. Most people won't know which group their children are in.