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 betwee n the magnitude of surface astigmatism and subjective estimates of una cceptable blur flanking the near zone of progressive addition lenses ( PALs). Methods. Eleven presbyopic subjects observed a row of capital l etters at a distance of 40 cm looking left and right within the near z one of six 2.00 D add PAL designs, stopping when they reached the limi ts 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 li mits of clear and comfortable Vision in the near zone of the six 2.00 D add PALs used in this experiment. Conclusions. Although the 1.00 D a stigmatic contour indicates the boundary of clear vision, there are a number of caveats associated with the 1.00 D metric including the infl uence of laterally declining add power on perceived blur.