title: Tscherning ellipses and ray tracing in aspheric ophthalmic lenses.
abstract: The effect of conicoid asphericity in one of the surfaces of an ophthalmic lens is examined by means of exact ray tracing. Graphical solutions resembling the Tscherning ellipses are obtained for lenses free of oblique astigmatism as well as for lenses free of peripheral power error or curvature of field.
mesh_terms: D004867:Equipment Design; D005139:Eyeglasses; D006801:Humans