I found this product to work as advertised. I tested it by simply alternateing glasses and the dioptrix, I found I could see the same detail without glasses with the dioptrix. The only suggestion I would make is to take the dioptrix to your optition and have them mark the inner ring for your particular degree of axsis. This allows you to orient the dioptrix without need to rotate back and forth to locate the clearest oreintation. Mine is 91 degrees so it lines up with the notches top and bottom on the inner ring. A small dot of white paint would work as well.