title: [Mathematical reflections on the use of the cross-cylinder (author's transl)].
abstract: The optical effect of the cross-cylinder in checking the position of the axis of a correcting cylinder-lens is based on the laws of obliquely crossed cylinders. The corresponding formulae are specified, since relevant calculations are more precise than graphic diagrams, especially for comparisons in tabular form. Some examples are given.
mesh_terms: D005139:Eyeglasses; D006801:Humans; D008433:Mathematics; D009885:Ophthalmology / Q000295:instrumentation*; D012029:Refraction, Ocular
vernacular_title: Rechnerische Betrachtungen zur Anwendung des Kreuzzylinders.