Part 3 discussed the effect of angle Kappa on PAL fitting. Part 4 addresses the effect of the dominant eye and alignment error on PAL success. A patient’s adaptive response is for the dominant eye to center on the clearest portion of the segment in the lens in front of the dominant eye. If the lenses are incorrectly aligned, the non-dominant eye’s visual axis will now fall outside the umbilic. That results in a head or eye turn to make near vision clear.

The very young can be quite difficult when taking a pupillary distance measurement.

POW or "position of wear" is a term that is used to describe the way that an eyeglass frame positions lenses in front of the eye.

Clinical Tip When fitting multifocals, especially in higher powered Rxs, although you normally place the MRPs or optical centers at unequal decentrations to agree with unequal monocular pd's, you may wish to equalize the decentration of the segs for a better cosmetic result.