In reply to aldo56:
When it gets drizzly and windy my glasses fog right up and I sometimes just give up and put them in a pocket. Sometimes if you get some nice mucousy spit and rub it over the lenses they work for a while (yum).
For alpine I have fancy prescription sunglasses (~85% and mirror coating). With my astigmatism lens curvature is a real issue, so go to a good eye doctor for them, it took a while to find me a suitable pair, but ended up with some motorbiking sunglasses with a removable "air dam" to seal around the eye. I also have a pair of photochromatic prescription sunnies for general outdoor use in California where it was bloody sunny. They go from yellow high contrast tint (~15%) to super dark (~80%, almost Cat 4). Both pairs are polarized which is good unless reading digital screens.
I climb in my normal glasses (summer and winter), but I have high impact lenses and all the anti-scratch coatings after needing to replace them after a bike crash and the optometrists people taking pity on me. I don't use any sort of cord, I've never had the things fall off. But I did climb once in my backup pair with old, heavy lenses and they felt noticeably less secure.
As far as steaming up, you need to get as much ambient air as possible to your face. No nose covering, ideally no hood. That usually works for me. I wear normal ski goggles with the most ventilation I could find, but have cut a small notch out of the foam on each side to relieve most of the pressure on the arms of the glasses.