Your eyes change shape as you age -- they get more "leathery". In my case, I had myopia from about 16 until I was 40, although I stopped wearing glasses a few years before I hit 40 because I found that I didn't really need them. My eyes are "rounder" now than they were when I was 16, and it will eventually go the other way and I will need bifocals / reading glasses.
Your body changes a lot around the 40 year mark and I don't think that it's related, at all, to your smart phone. I'm sure that those older than us can tell us what to expect in the next decade.
I'm not sure if scleral remodeling the reason. My understanding was that the lens part of your eye became less elastic as you aged, you can't focus as near, and you became more farsighted as a result - a phenomenon called presbyopia. Thus, if you were nearsighted before, you'd be closer to regular vision or maybe even a little farsighted, needing reading glasses to focus closer up.
Your body changes a lot around the 40 year mark and I don't think that it's related, at all, to your smart phone. I'm sure that those older than us can tell us what to expect in the next decade.