Ha Ha ! I think we have a conflict between an well educated, highly trained and well respected sports optometrist and a shotgun coach who is marketing a contraption which clamps onto your gun with the expressed aim of over coming an eye dominance issue. I feel sorry for the guy who is probably a great coach but just a belligerent troll on forums. By the way I'll stick with a bit of tape over the lens of my shooting glasses rather than the contraption... sticking your thumb up would have a similar effect to the opaque plastic plate