I have a pair of RUdy Project Horus with swappable lenses but they definitely look like sporty/cycling glasses. When I wear them to the gorcery store, etc. I always feel a little weird.

So this summer I got a pair of Spy Kash sunglasses with Rx lenses, they look casual enough but have great coverage. I have done a few 30+ mile rides and they work just as good as the RPs.
I would think a pair with Transition lenses are what your're looking for, if you like the syle.