Myopia (or short-sightedness) is caused by the eyeball being a bit lopsided; The front of your eye (lens )to the back wall (retina) is too long, more specifically.
[This picture demonstrates](https://thumbs.dreamstime.com/z/myopia-myopia-corrected-minus-lens-eye-vision-disorder-76424428.jpg) why things are blurry at a distance.
Spending time reading or watching screens causing it is an old wives tale.
As far as your follow up questions:
1) Challenging your eyes at longer distance will do nothing to help, and may fatigue the focusing muscles in your eye after a while.
2) Wearing glasses or not won’t worsen myopia, but will make you more aware of the difference of corrected vision vs non-corrected.
Latest Answers