Mine are polarized prescription, single vision, in 14K gold plated Italian frames, with a single-piece nose bridge and REAL GLASS lenses...none of this plastic or resin crap for my sunglasses. Very close-to-the face frames that block out most of the side-entry sun rays. I really do not like to shoot photos wearing sunglasses, but I have a few times. I wear them mostly for river and saltwater salmon fishing,where the UV rays can cause eye damage, and to alleviate eyestrain on open water.
If you wear cheap sunglasses that can not filter UV rays, you're really not taking proper care of your eyes. Opening UP the pupils by putting cheap sunglasses in front of your eyes then blasting your wide-open eyes with UV rays...NOT good. THis is especially bad for kids; do NOT let your kids wear CHEAP, non-UV protecting sunglasses. Ever. At least that's what my eye doctor has been telling people for 30 years.