I often thought that glasses and people who do a lot of reading etc was a side effect rather than a cause - i.e. that people who read more noticed they needed g

I often thought that glasses and people who do a lot of reading etc was a side effect rather than a cause - i.e. that people who read more noticed they needed glasses and we're happy to wear them, but kids who would rather do sports perhaps didn't notice so much and/or were less inclined to wear glasses when playing cricket or whatever