I had a similar situation/concern a few years back… went to Dr and Optician got glasses, light therapy etc. No improvement and became exasperated.
What solved the mental focus for me was light movement while reading (walking on treadmill etc) and/or laying down to relax most core muscles. Second, shockingly NOT chewing gum or doing too much downward facing iPhone reading made a massive difference to my vision.
Causality? The impact of posture and/or movement on breathing has a big impact on brain focus. If you have a blood O2 meter you can test this while your are reading. Ironically the more worried you become about not focusing the more you hold your breath and the more clenched your posture. It’s a vicious cycle.
Gum was the shocker, I would habitually chew in the morning for an hour or two (mindlessly) and it turns out it was over taxing the jaw and neck muscles. This caused the eye muscles to be impacted and resulted in blurry strained vision. Cutting out gum for a week almost entirely removed my need for glasses. Lastly, I would still get blurry vision occasionally and finally narrowed it down to iPhone “texting neck”.
I’ll post a couple of refs in a minute. May be unrelated but if there’s a thread to pull on here I hope it helps.
Anyone wanting to understand the “why” behind this is encouraged to read Ray Dalio’s latest book. As the worlds largest hedge fund his firm put big bets against Europe last year and doubled down more this year. There are generational macro effects that make this far more predictable and yet uncontrollable at play. Also checkout Peter Zeihan’s book that briefly made it to the NY top 10 a couple of months back. Both have done the scholarly work so you don’t have to…
Principles for Dealing with the Changing World Order: Why Nations Succeed and Fail https://a.co/d/glYQyNV
https://news.ycombinator.com/item?id=24102829