Relationship between contour plots and the limits of "clear and comfortable" vision in the near zone of progressive addition lenses.

PURPOSE: The aim of the study was to determine the relationship between the magnitude of surface astigmatism and subjective estimates of unacceptable blur flanking the near zone of progressive addition lenses (PALs).

METHODS

Eleven presbyopic subjects observed a row of capital letters at a distance of 40 cm looking left and right within the near zone of six 2.00 D add PAL designs, stopping when they reached the limits of "clear and comfortable" vision. Eye rotations were measured by video-based pupil and corneal reflection tracking.

RESULTS

There is a good correspondence between the 1.00 D astigmatic contour and the limits of clear and comfortable vision in the near zone of the six 2.00 D and PALs used in this experiment.

CONCLUSIONS

Although the 1.00 D astigmatic contour indicates the boundary of clear vision, there are a number of caveats associated with the 1.00 D metric including the influence of laterally declining add power on perceived blur.