Go to lenscrafters or D.O.C. at the mall and get a prescription. Usually about 80 bucks. It's the biggest fucking waste of money ever, especially since my prescription hasn't changed in over 10 years. I have to do it every year, after I forget that my prescription's lapsed and I can't get any new contacts.
I like to refer to it as the "eye tax".
One thing you can do, and I've done it before, is scam a "trial pair" of contacts from the eye doctor. I've been in a situation where I had to go to work (as a bartender... BAD idea if you can't see anything), but had no contacts... I pressured the eye doctor into giving me a trial pair that was very close to my presription and a different brand than i usually get even though they didn't have any of my prescription contacts available. Saved my ass.