If you're thinking of focusing issues, IIRC there is evidence that not getting exposed to enough UV light (read: sun light) during years our eyes develops may play a big part in that.
No idea if that would imply this is needed as an adult though. And that is assuming I don't misremember in the first place.
Yes focusing eyes close all day is the real culprit. But there is something about bright light of monitors that seems to impact my vision too, i am not quite sure what its callled though. I don't feel the same fatigue reading a book. Its just my personal experience.