Sports sunglasses and highly aerobic winter activity

I'm writing to pick the brains of opticians and athletic types on this
one. There's a current discussion on rec.skiing.nordic, primarily a cross
country ski racers' newsgroup, about prescription sports glasses, skiing
and fogging. It's a common problem when the aerobic (and anaerobic) skier
stops on cold days, and deadly in races. I have been using single-vision
inserts for Bolle Paroles and Rudy Project glasses for a few years, and
have adjusted the nose pieces and inserts to create maximum breathing
space, but that just seems to buy more time. One skier reports having had
an optician replace the lenses on wraparound snowboard glasses with
Transitions, adjust the frames a bit, and then use some anti-fog spray. He
reports an improvement, but not total satisfaction. Are single lens
glasses with factory anti-fog any better? Anything to know in choosing the
best kinds?

Gene Goldenfeld