Four eyed velocipedalists?

don't really seem that cheap, when you can get a good second hand pair of oakley's and get your optition to swap out the lenses.

I wear lenses most of the time, but sometimes wear glasses. Last year I bought a pair of oakley prescription glasses, which have the same kind of "stem" as their sunglasses and the rubbery nose pad things. http://oakley.com/pd/1149

They don't slip at all, even when I sweat. I have been back to the optician once to get the stems tightened, otherwise they're the best specs I've had - but not cheap.