Hi all - a quick question that I'm sure has a quick answer: Is there a difference between "Prescription Frames" one might find in an eyeglass store and the frames that come with Oakley's sunglasses? In particular, I'm looking for an old pair of Square Wire 2.0 silver frames. I see sellers (on eBay for instance) selling Square Wire 2.0 sunglasses, and I see others selling Square Wire 2.0 prescription (Rx) frames. Is there a difference? Can I put a pair of sunglass lenses in prescription frames? Thanks!