How about some protective safety glasses/goggles made for people to put over their prescription glasses? Like if you are going to mow the lawn or use a power saw or something? I hear they have nice new styles these day.

Or if you don't mind tinted sunglasses, there are some I just got that I like and wear over my prescription glasses when biking. Totally keeps the wind and bugs out- plus it protects my expensive eyeglass lenses.