Per Ralph Mowery:
What has that to do with safty glasses ? They do make them as just plain
lenses. I wore them for years at work. Also for some jobs around the house.
Goggles for the weedeater.

Almost all prescription glasses now are some kind of plastic - so they
function as safety glasses. Probably not as well as dedicated safety
glasses depending on the lens size... but they do offer protection
against stuff flying into the eye.
--
Pete Cresswell