Cycling glasses typically wrap close to your face to keep wind from getting behind the lenses, which can really irritate your eyes. Ideally, they'll also do a better job blocking light around your peripheral vision (especially at the top) than, say, a pair of Wayfarers.The lenses are usually made out of polycarbonate plastic, which is less likely to shatter. Admittedly, polycarbonate is pretty common with sunglasses in general these days.The very earliest Oakleys (which I think of as the progenitors of the whole cycling-glasses genre) even had a foam pad along the upper edge to keep sweat out of your eyes.