I watched a Japanese doc about this phenomena a couple years ago. Japan's genetics haven't changed in recent decades but now basically everyone leaving highschool needs glasses. So they strapped lasers to kids to measure the distance in front of their face, to track their focus distance throughout the day. The results and outcome were telling, suggesting a conflict of cultural standards regarding eyesight.

The worst, closest, time was while at school. The kids were learning writing, Japanese characters. They were sitting at desks, their heads looking straight down onto paper as they learned to create tiny perfect characters. But at the doctor, the kids were given eyeglasses to correct their vision to the 20/20 western standard which itself is largely based on operating vehicles or seeing blackboards in giant lecture halls. So kids with glasses optimized for distance were forcing their eyeballs out of shape to focus on schoolwork literally inches from their face. The finding was that perhaps Japanese eye doctors should prescribe glasses based on what kids actually need (close focus) rather than pretending they all are going to be driving cars and flying planes.