Very useful thread - this. Once again Pprune scores over the magazines.
I also have reached the age where reading glasses are needed. I also had a pair of (very natty) tinted varifocals made up. I only wear these for flying or driving. I find them great but with one important caveats - they make distance judgement when taxiing VERY tricky. I now will not taxi with them on, having experienced an unfortunate case of self-inflicted hangar-rash. Apart from that I find them great in the air - making reading easier, instruments easier to read and vision outside fine.
I do wonder, now having read this thread, whether my roundout is affected glasses off and glasses on and I am going to try, carefully, some experiments to see what effect the glasse have in the circuit. Another intrepid airman will ride shotgun during this experiment, needless to say...