Let me preface this with my qualifications;
I am an Optican, and former Optical Lab Tech. I've made glasses, I've fit and dispensed them, and I've shot them. Yes, SHOT them.
Polycarbonate dress lenses are sufficient protection for
most shooting applications; Indeed, most safety glasses these days use polycarbonate lenses. The only difference between dress lenses and safety lenses is that dress polycarbonate lenses lenses have a minimum thickness of 1.0mm (ANSI Z80) and safety polycarbonate lenses lenses have a minimum thickness of 2.0mm. (ANSI Z87)
All other materials (CR-39, Flint and Crown Glass, HIP (Hi-Index Plastic) and Trivex) have a safety glass minimum thickness of 3.0mm.
When I was a lab tech, I used take the defective poly lenses (what defects, you ask? Mostly coating defects, and some carbon flecks in the lens. Those have been eliminated since then.) out and shoot them with various guns.
Here are the results:
.22LR, fired at 10 yards- bullet would stick halfway thru. I used one as a demonstrator at work.
.38 wadcutter, same distance-same result, wouls stick in lens.
.357, sailed right on through.
.44 Mag.-found lens fragments 20 yards away.
Shotgun, 30 yards. Dented, did not stick or penetrate.
Shotgun 50 yards, light dents. Same results.
I had shot ricochet off a plywood board from a .410 once, hit my glasses (poly lenses, of course) and dent them.
I wear dress thickness (granted with my Rx, they are only thin at the OC, thick everywhere else!) when I shoot, mostly because I don't walt to shell out for Sawflys or ESS with the inserts (I have a high minus Rx-it wil not fit in most shooting glasses frames without inserts) and I'm not worried about it.
By federal law all eyeglass lens have to withstand a 3/4 " steel ball dropped from a heght of 40 " IIRC.
I used to get my glasses from work also and learned one lesson polycarbonate may be impact resistant but even with an anti scratch coating still scratched very easily. And polycarbonate in impact resistant but not bullet proof.
Only Glass lenses have to be tested individually; 5/8" ball for dress 1" ball for safety; all other materials are 'representative' batch tested; ovbiviously, if every poly lens were tested, they'd all be dented; as you discovered, poly is impact resistant, due to the cubic molecular structure of poly, but it is soft as far as sratching is concerned.
Fun fact; pouring a little acetone on a poly lens will cause it to crack instantly.