I've always worn safety glasses over my prescription glasses for shooting. My prescription glasses are thin and don't provide much coverage, especially coming from underneath. Also, they cost a lot of money and I really don't want to deal with scratches on them due to getting hit by brass or jacket ricochets off of steel.
This link provides a good overview of the need for real safety glasses as opposed to cheap plastic sunglasses or glasses with glass lenses:
An alternate option is to get prescription safety glasses, which I'm looking into, but from what I've seen in my searches, it's rare to find any that are made in my prescription, which is very nearsighted. Also they are expensive, and I'd need to get both clear and dark versions, or figure out some kind of clip on sunglasses system.
What I've been running so far:
Escort safety glasses:
They also make these with smoke colored lenses for bright outdoor shooting:
These glasses work well but the black frame obscures peripheral vision a little.
Another alternative that I've found to work well is Pyramex OTS safety glasses:
which also come in clear or dark.
Both options above were comfortable, gave good coverage, and seemed optically clear to me. But I have been thinking that perhaps a more expensive set of safety glasses would have better optical clarity which could come in handy.
Cocoons Eyewear seems to fit the bill, although I have not tried them yet.
Note that the lenses are not advertised as meeting any safety standard such as ANSI Z87.1.
Finally, a tip from experience: if you leave your safety glasses in your shooting bag, make sure to put them in a separate compartment, or in a bag or case. Left loose in the bag, they will get scratched up by other things in the bag, even though they're supposed to be tough and scratch resistant.