I had myopia from when I was a teenager. I didn't realize it till I was 21 and tried glasses and could suddenly see what I didn't know was possible to see. I then wore glasses from 21 to 27. Quit wearing glasses at 27 and left the office and computer to be mostly full time in the woods. Two years later my myopia had mostly reversed and I could see crisp detail at long distances without glasses for the first time. Six years now since I noticed the reversal and I still can see clearly at long distances. I love it.
Summary. "The human eyes are continuously adjusting refractive power, vergence angle, and pupil diameter when exploring the visual environment. Adjustment errors in these visuomotor functions reduce the stimulus contrast driving ON and OFF retinal pathways, and ON retinal pathways become weaker, slower, and less sensitive in refractive disorders such as myopia. Here, we demonstrate that, in addition to these sensory deficits, myopes also have deficits in visuomotor functions driven by ON and OFF pathways during lens accommodation. We show that humans with myopia have excessive accommodative eye vergence with reduced ON pathway dominance and excessive accommodative pupil constriction. The excessive accommodative pupil constriction that we demonstrate could potentially weaken ON pathway responses and cause ON pathway deficits. This mechanism could explain why myopia increases with activities that maximize accommodative pupil constriction, such as near work, and decreases with activities/treatments that reduce it, such as outdoor activity, atropine, positive defocus, and low contrast."
It's because you focus on nearer things much more time than things which are far away. One does not need a PhD and the whole kitchen sink to notice that.