"Oh ya, take heed to WarrenD's advise; don't wear them while outside in the sunlight and possibly fry your face off!"
Oh yes, another thing to watch out for. The friend who turned me on to the Mag-Eyes used an Opti-Visor too. He related this to me:
He was in the middle of a modeling session, and was really in the "zone".

He, or his SWMBO, decided that a run to the local jiffy/quickee-mart was in order, so he jumped in the car and ran into town. Went in, got his stuff, all the while getting stares from people in the parking lot, and in the store. Came home. Realized, after getting home, that he still had his Opti-Visor on, but flipped up.

THAT'S modeling concentration!
BTW, I got my set of Mag-Eyes at Hobby Lobby, and it came with two lenses. FWIW, HTH, YMMV,
Warren