Abstract

During the past few years spectacle lens manufacturers have been remarkably successful in improving the optical properties of progressive lenses. However these lenses still have astigmatic, prismatic and other refractive errors in the peripheral area of the narrow transitional middle corridor. These problems are tolerated in the interest of the more important aim of correcting the presbyopic eye with one lens for all distances. The errors manifest themselves as magnification differences, image distortions, image tilts and reduced visual acuity. During the development of new progressive lenses, manufacturers have tried to make the increase of these errors as smooth as possible. However, there are still quite a few questions open concerning the physiological effects of refractive errors associated with these lenses. For example, it has still not been determined to which extent the unwelcome side effects may impair fusion and binocular vision and which errors may be tolerated. Another important question which has evoked discussion is whether the binocular system reacts differently to equal optical impairments as compared to different impairments presented to both eyes.

© 1991 Optical Society of America