Hi, is there any difference in vision when compared to essilor's crizal 1.67, zeiss clarity AS 1.67, hoya's 1.67 nulux as well as a standard 1.67 hmc lens. I do know that the multicoat applied to the lenses are different, but is there any difference in the vision seen by the px? Another qn will be is zeiss individual a single or double aspheric lens design?