my $.02
I recently bought new glasses, so I just wear my old ones to ride (with one of those reallly cool "sporty" straps). I also always wear a helmet with a visor to keep the worst of the sun out of my eyes.
b.t.w. the strap mabye lame as heck but I just had a little spill, broke my helmet visor, and a rib but kept my glasses securly on my melon.