Way back when I was about half the age I am now my eye doctor told me to do eye exercises. To hold my thumb up, focus on it then focus on the far wall. This was to strengthen the muscles that focus the eye. I don't think I ever did it. You know how a smart alec in his thirties thinks.
Well thirty some years later I was sitting outside my camper reading a western novel. I looked over on the far side hill and every thing was a blur. I stared at that side hill untill it came into sharp focus, but when I looked back at the book, it was a blur. So I stared at it untill I could read a paragraph then looked at the side hill blur again, and stared at it untill it was sharp. Now I didn't have to keep this up too long untill I could look back and forth and the book and side hill were both sharp as soon as I looked. As a matter of fact it wasn't too long in this first session that I got so I could read 2 or 3 pages and the side hill was still sharp. That was 3 years ago and I still do a session as described every once in a while and today after wearing bi-focals for 27 years, I can read a western novel without my glasses.
And this year I passed the eye exam for my drivers license renewal without my glasses, first time in 52 years.