I'd go along with all the comments regarding having scratch-free and AR-coated lenses, and for keeping your windows (outside AND inside - the thin and barely visible film that slowly builds up on the inside can cause more scattering of light than any obvious drt on the outside...) spotless.
I recently replaced some 5-year-old glasses, and despite there being no change in the prescription, the difference in clarity between old and new lenses was startling. I knew the old lenses were a bit scratched, and the AR coating was wearing off around the edges, but I hadn't realised just how degraded my vision had become, so slow had been the change. The first time I put on the new glasses, everything looked so sharp and bright, it almost hurt... I'd put up with a bit of dazzle when drivng at night, thinking it was just the way it was, but these new lenses have all but eliminated it.
On a semi-related note, do any other glasses wearers find certain colours get shifted left or right depending on whether you look at them through the centre or edges of your lenses? Mostly seems to affect the red end of the spectrum for me-makes for some interesting effects when looking at red-ringed roadsigns out the corner of my eye... at/above a certain distance from the VSL signs on the M25, I can shift the red ring far enough such that the limit numerals are no longer inside. Not that I'd ever consider using that as a defence against a speeding charge
