Worksheet 9: Oblique Meridian Formula.
Back and Front Vertex Power.

Oblique Meridian Formula

  1. The power on the horizontal meridian for the Rx +1.00 -2.00 x 050 is

  2. The power on the vertical meridian for the Rx -2.00+2.50 x110 is

  3. For the Rx -5.00 -1.50 x145, the power on the 36th meridian is

  4. If the Rx is +1.25 -2.50 x025, the power on the 70th meridian is

    5. Front and Back Vertex Power

    If the front surface is +8.25, the back surface is -2.25, the thickness at the optical center is 15mm, and the lens is made from 1.80 glass, what is the

  5. nominal power?
  6. front vertex power?

  7. back vertex power?

  8. If you put this lens in the lensometer with the concave side to the lens stop, and the convex side toward you, what power would the focimeter power wheel show?


  9. If the front surface is a +14.00, the back surface is a -4.00, the lens is made from 1.523 glass, and the thickness is 5.5mm, what power would the glasses wearer be experiencing?

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Textbooks:
Brooks & Borish, Systems for Ophthalmic Dispensing, 2nd Ed, Butterworth-Heinemann, 1996
Stoner, Optical Formulas Tutorial, Butterworth-Heinemann, 1997

Copyright 1998 - 2001, Ellen Stoner, MALS, ABOM, NCLC
Registered students may print one copy for study purposes.