title: Unwanted astigmatism in lenses with a concentric variation in sagittal power.
abstract: A concentric variation in sagittal power, Fs, with zonal radius, y, has been used in some designs of varifocal and aphakic spectacle lenses. It is shown theoretically, using a paraxial approximation, that a gradient dFs/dy in sagittal power leads to the introduction of an amount y.dFs/dy of unwanted astigmatism. The validity of this result is illustrated experimentally.
mesh_terms: D001036:Aphakia, Postcataract / Q000628:therapy*; D001251:Astigmatism / Q000503:physiopathology; D005139:Eyeglasses / Q000592:standards*; D006801:Humans; D007834:Lasers; D008962:Models, Theoretical; D055095:Optics and Photonics / Q000295:instrumentation