Why Do So Many Kids Need Glasses Now?

Kids ain't getting outside enough.

I'm afraid we'll be in that boat too. My toddlers walk outside every day but it's harder in winter.

animals that operate in the dark tend to have bad vision

their counterparts that operate under the sun tend to have good vision

is there causal effect? or just correlation that light intensity matters?

I want to think it's this. My anecdotal data point is I was outside nearly every day as a child and I assumed my vision was fine. It wasn't until 2 years into university that I had my vision checked and got my first prescription and it was night and day better. I imagine there's a great deal of people that don't know they should get prescribing correction glasses.

I have a theory, I think the problem is the lack of range of eyes muscles. Most people who needed glasses are people who are not usually seeing long distance objects, these people usually stays in a confined space or usually reading or using cellphones, eventually the muscles used to focus objects becomes limited in range of motion. Imagine a camera who cannot focus, because of a failure resulting in a limited range of motion. Despite having no problems with the lenses, the camera remains out of focus this resulting in blurriness. I do think people need to get out, see long distance objects, not just remain in a confined space with close proximity objects like walls,etc. My vision returned to 20/20 after ditching eyeglasses and going outside, and if I am inside the office I picked location near windows and relax my eyes looking at distant objects.