Description
Progressive addition lenses (PALs) have now been available for over 40 years, and are now an accepted form of spectacle lens correction for presbyopia. The characteristics of typical generalpurpose designs are described, using aberration power plots produced from lens measurements and a simple predictive computer model. Some of the effects of using high refractive index materials, and also the impact on aberrations of short and long corridor designs, are also described. There is also a discussion of the problems in relating lens wearer trials to measurements of lens aberrations.
