Here is the question:

Rx

O.D. -2.25 -1.50 x90
O.S. +0.25 -1.50 x90

Add +2.00

Natural PAL

Slab off O.D.

As a result of the aniso, when the presciption is ordered with no prism, there is a small amount of induced vertical prism at the fitting cross. The induced prism measures 1^ base up O.D. as the distance from prism dot to fitting cross in 4 mm. In an effort to eliminate this vertical imbalance at the fitting cross that the patient doesn't need, we're going to order the prescription with 1^ base up O.S. We chose this route instead of ordering 1^ base down O.D. to keep from increasing the edge thickness O.D. And.. a little yoked vertical never hurt anyone. :)

The problem is with the slab-off and our understanding of standard lab protocol. The goal is to eliminate all binocular imbalance of vertical prism at near. In order to do so, the lab should leave 1^ base up O.D. under the slab. If all prism is eliminated under the slab, the patient will be left with an unwanted 1^ base up O.S. What do labs usually do...eliminate all vertical prism or maintain any vertical ordered in the distance?

Also, can someone tell us (with a PAL) if we can order the slab at any height we wish? Thanks in advance for any help/advice!

Robert Wagner (chief optician and fireworks master)
Beaverton, OR