Its important that the sunglass block UV - A and UV - B. Otherwise you are allowing the eye to open up and let all that UV into the inside of the eye.
The Ray-Ban marketing department makes a big deal about UV protection, but the fact of the matter is that plastic (and glass) that transmits UV light is more expensive than plastic (and glass) that doesn't. All sunglasses, even the cheap ones, do a more than adequate job of blocking UV-A and UV-B light.
