Using the latest computer-driven
  equipment and proprietary software, the
  back surface of every Digital lens (closer
  to the eye) now contains 100% of the
  patients Rx. (sphere, cylinder, axis, prism,
  and add power) while the front surface is
  a perfect sphere.

  This revolutionary technology eliminates
  the "Swim and Sway" associated with
  conventional progressive lenses. Digital
  backside progressive lenses are superior
  to conventional PALs in every way and
  provide your patients the optimum vision
  solution while distinguishing your practice as
  a provider of the latest technology.