1) "So can you really not see ANYTHING without them?" No, but the one thing that I really cannot see with or without my glasses is the point of your question.
2) "Wow! You really are blind. I can't see anything when I put on your glasses!" Thanks for validating my blindness. You're very dear to me now.
3) "But you'd look so pretty without them..." And you'd look soo pretty just a little further away from me...just a little bit more...just move over to the next state, yeah that's better.
4) "Are you one of those people who wear glasses because it looks cool?" You got me. BTW Congratulations on your appointment as the 'Judge of All Things'.
5) "Have you heard of contact lenses?" WHAT?! What futuristic nonsense are you spewing out, good sir? *adjusts monocle*
6) "You're so lucky, you don't even have to bother with eye make-up" GUYS! This one has cracked our secret. The reason why we're always so happy... no smokey eye struggles!
7) "How do you watch 3-D movies?" Yes, that is the question that keeps me up at night...Will I ever enjoy Avatar as it was meant to be?
8) "You must be so intelligent and probably study all the time" Yes, I got these glasses as a result of study marathons and not reading Harry Potter with a torch under my blanket for hours...studies...!
9) "You can obviously see better than all of us right now, right?" Obviously, my prescription glasses have given me super human visual strength and I can literally see the angels facepalming at your questions.
All said and done, and as Matt Smith puts it, glasses are cool!