Design Philosophy For Moderate Plus And Minus Power Aspherical Lenses

Abstract

Classification 1. Application Aspects: 1.1 Aspherical lenses designed mainly to improve the peripheral imaging quality. Such aspherical surfaces are used when the effects of bending no longer lead to success in the high plus range over (+8 D). 1.2 Aspherical lenses designed mainly for cosmetic purposes. Such aspherical surfaces are used in the high minus power range below (-8 D). From the corrective center area towards the periphery there is a continuous transition of the surface in order to flatten out the steep concave curvature. In this process the edge thickness is reduced dramatically. The lenticular design here does not, however, have any steps or edges and so offers a better cosmetic appearance than conventional lenticulars. 1.3 Aspherical lenses with a continuous power increase. Such lenses are termed Progressive Addition Lenses (PALs). They are designed for a comfortable correction of presbyopia and have the advantage of showing no optical discontinuities over the whole visual field. 1.4 Aspherical lenses with increased comfort in wear. In the moderate power range, ametropes can indeed be provided with a truly satisfactory correction using the standard solution of spherical surfaces. If, however, aspherical surfaces are used, then the wearing properties can be improved to a large extent. By wearing comfort we mean the result of harmonizing such different characteristics as the imaging properties, the weight and the cosmetic appearance. The optimization processes provides for the reduction of center or rim thickness, for a lower bending (so that the lens apex will no longer protrude so far out of the frame plane with larger eyeshapes) and at the same time the optical quality of the spherical standard should be maintained or even improved.