If you are concerned Revision combat glasses have a prescription insert. I still have mine from the military. They are excellent all round eye protection without sacrificing vision.
They don't enfore glasses-over-glasses here, but yeah, normal glasses don't offer that much protection.
I've gotten 'hit' by some carbon fragment a couple of years ago and it scratched a big part of the cornea... I was wearing normal glasses at the time. It hurt for a long time, and i could feel the severe itching sensation for years afterwards.
+1 for the revision pro-wear. A couple of eye places here in Ottawa can make the lense inserts for 100$ IIRC.
Do range rules these days typically require safety glasses over top one's regular eyeglasses?
EDIT: Thanks so much for your replies, everyone!