I've tried this before and I was disappointed. I ended up buying three different (cheap) pairs on Amazon and trying them on at home. I guess it wasn't a complete waste of time, because I liked one of them and bought two more of the same brand!
Is there a line you like specifically? Oakeleys, Ray Bans, Quays? I would narrow down brand and search on the vendor's website and then compare to other discounted outlets like Nordstrom Rack or Amazon. I personally love these as they are sleek and subtle.
I'll have to check Warby Parker out- I am very light sensitive (photophobia) due to my severe chronic migraines and live in sunglasses. Finding affordable prescription sunglasses so I can simply go grocery shopping or go out for gas is a must in my life LOL. :) Thank you!