>>wearing sunglasses that block ultraviolet (UV) rays to protect your eyes.

As I understand it, pretty much all materials used for Rx lenses (Glass, Polycarb, Trivex ,any High Index - but not CR-39) block UV-A and UV-B simply from the nature of the material. If you're getting CR-39, expect your optometrist to push a UV coating pretty hard. In my state, it's required. No idea about yours.

I didn't list UV-C as it doesn't make its way through the atmosphere to the ground. Astronauts are on their own here :-)

This is an excellent reason to avoid super-cheap plastic-lens sunglasses. Think about it. Bright sunlight (plenty of UV) but you're not squinting, your irises are open appropriate to a lower light level - and the UV is pouring in.