Neutralizing Progressives with Prism Thinning

July 21, 2016

Before we talk about neutralizing the Rx, let’s review some of the basics of prism thinning.

  • Prism thinning is adding prism to an Rx that results in a more cosmetic appealing pair of eyeglasses.
  • The prism added will be the same amount and in the same direction in the pair of lenses.
  • The amount of prism added will be determined by the Expert’s Optimal Prism Thinning software.
  • The software analyzes all the parameters of the Rx- powers, measurements, and frame to determine the amount of prism that would work the best for the pair of lenses.
  • The amount of prism thinning will be limited to the successful patient adaption results in studies.


Reading the amount of prism thinning is quite easy. The most important part is positioning the lens in the correct position in the lensometer. Prism in a progressives are read at the Prism Reference Point (PRP)


To determine the mount of prism thinning:

  • Remark the lens with the PRP dot.
  • Physically looking at the lens- not through the lensometer.
    • Align PRP dot to the middle of the Lens Stop.
    • Fine tune the alignment by bringing up the Marking Pens to align the center pen to touch the PRP dot.
    • Bring Lens Table up to support the lens/frame with the PRP centered.
  • Look in the Lensometer and note the center position of the mires on the reticle’s vertical prism rings. This reading will be your prism thinning amount. Both lens should have the same amount in the same direction.

This prism thinning amount is important if you are ordering a one-lens remake/replacement. Please request it on your order. Or you can also write the other lens prescription and mark “FOR INFORMATION ONLY”.


Robert Hughbanks ABOC, HOAA- Manager of Training and Development