For my medicals I wear my contacts just because most of the time I wear my contacts when I fly. It shouldn't really matter because on your medical it will say "Holder Must Wear Corrective Lenses" if you wear glasses or contacts. It will be wise however to have your pair of glasses with you when you fly, I even believe it's regulatory if you wear contacts. If you want to wear your glasses that's fine also, it won't matter during the physical.