Performance of aspheric spectacle lenses

With improvements in spectacle lens technology, several aspheric lens designs have become available in the moderate power range for prescribing by ophthalmic practitioners. Their manufacturers claim that these lenses improve cosmetic appearance and are lighter than equivalent spherical lenses, without sacrificing visual performance attributes such as good off-axis visual acuity and low distortion. We have made measurements of aspheric lenses made by Rodenstock, Essilor, Sola and Hoya, and have compared them with spherical lenses which have minimal off-axis power errors (best form design). Our results generally support the claims. Cosmetic appearance is considerably better for aspheric than for spherical lenses. The reduction in weight for plastic aspheric lenses is 8-32 per cent for 60 mm diameter. The percentage reductions would be less for smaller lenses. Except for a few exceptions, off-axis power errors of aspheric lenses are similar to those of similar power spherical lenses. All the aspheric lenses have similar or less rotatory distortion than spherical lenses of similar power