Parts 1 through 4 of this series described the importance of determining the visual axis measurement to maximize patient visual comfort and satisfaction with PALs. This final installment introduces methods and devices to obtain that measurement.
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.