RECENT TRENDS IN PROGRESSIVE POWER LENSES

Despite having been first marketed in the 1950s, new designs of progre ssive addition spectacle lens continue to appear, Some of the recent p atent literature is reviewed on the design of such lenses, As well as a number of improvements to general purpose designs, specifically to i nclude aspheric surfaces for the distance portion of progressive lense s, the literature includes a recent patent on an improved version of t he Alvarez lateral translation lens system, The optimisation of single vision lens forms in order to extend the depth of field for early pre sbyopes is also discussed, (C) 1998 The College of Optometrists, Publi shed by Elsevier Science Ltd.