There was a neat little clop on loupe that came with 3 lenses + .5, + .75 and +.1 this allowed you to tune your glasses to the best sight picture. The loupe was n a spring loaded swivel and could be raised out of vision when not in use. It was called Clearsight. What I really liked about it was with different lenses you could tune for pistol or rifle front sights. Some would take 1 lens off of flip up sunglasses to blind the off eye helping the shooting eye to focus. As far as I know the Clearsight unit is no longer made. It was a handy unit in that it just clipped on the regular glasses bow and wasnt noticed.