When I first got my contact lenses many months back, for a long time I absolutely could not tell if they were "the right way" or inside-out. The lenses haven't changed. I still can't really look at a lens and tell you if it's inverted or not most of the time. The difference is that I just kind of intuitively know now. My perception has somehow changed to be able to identify the state of a contact lens, even though I can't really consciously tell the difference most of the time.