JPS5485742A - Spectacle lens - Google Patents

Abstract

PURPOSE: To improve wearing feel of variable focal spectacle lenses by providing normal distortions which are respectively long in the horizontal direction in the upper region along the main meridian and in the perpendicular direction in the lower region and providing an umbilical point having no astigmatism at nearly the intermediate point.

CONSTITUTION: The variable focal lens having a long-sightedness correcting position F, a medium vision correcting position P and a near-sightedness correcting position P and a near-sightedness correcting position N is so formed that the changes in the refracting power along the main meridian M-M' thereof become as shown in a solid line (m) and that the refracting powers in the direction where the deviations of the refracting power from those shown by the solid line (m) at each point on the main meridian M-M' become as shown by a broken line S. Here, ΔP denotes the astigmatism at the top and bottom end of the variable focal zone and provision of permissible astigmatisms along the main meridian M-M' where the frequencies of use are highest enables the astigmatisms on the side of the variable focal positions P and near-sightedness position N to be reduced, the differences in curvatures in the horisontal direction of the long-sightedness position F and near-sightedness position N to be reduced and the distortions and fluctuations of imgaes to be reduced.

COPYRIGHT: (C)1979,JPO&Japio