"Rain-X makes an anti-fog product. It's made for the inside of windshields and does the opposite of the original Rain-X. The inside product decreases surface tension on the glas so water sheets instead of beading. This product can be used on glasses (not on anti-reflective coatings!) to reduce fogging and rain beading. Apply it to both sides of the lenses."

I bought some of this over the weekend and put it on my plastic Oakley ‘m’ frame clear lenses. I am very impressed. Fogging has been about 90-95% eliminated and I see no ill effect on the lenses (yet).