Selective Blindness

One thing I've noticed, now that I'm using the computer/music room as an office & drawing desk for plans, is that I keep swapping between different reading glasses, depending on what I'm doing

For drawing & reading, I use my current prescription, which I think is about 2.5x magnification... but when I switch my attention to the computer screen in front of me, I switch to an older pair of about 0.5 less magnification, otherwise I get a little ocular distress - not pain exactly, but my eyes aren't comfortable reading the screen at the higher level. Which is weird, because when I was working at my former Debtors Prison, I needed the more powerful lenses for everything - reading, computer & plan-drawing

I'm sure the simple answer is that my home computer screen is a bit further away than the former workplace one & the angle of view is a little different, so I don't need the extra help from the glasses. Either that, or my eyes are slowly, magically regenerating themselves... which I somehow doubt