Vertex power

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The optical effect of spectacle lenses can be indicated with the vertex power . The vertex refractive power is the reciprocal of the focal length , i.e. the distance between the focal point and the vertex of a spectacle lens. The vertex power is usually given in the unit dioptre .

For the quantities of focal length or refractive power that are obvious when describing optical systems , the distance between the focal point and the respective main plane must be measured. In the case of spectacle lenses, however, their position is shifted from the center to the more curved surface and is not precisely known. A simple reference point is given with the eyeglass lens vertex; the vertex refractive power can then be determined with the aid of a vertex refractometer by measuring the focal length.

literature

  • Bernhard Lachenmayr, Dieter Friedburg, Erwin Hartmann , Annemarie Buser: Eye - Glasses - Refraction. Schober course: understand - learn - apply. 4th, revised edition. Thieme, Stuttgart et al. 2006, ISBN 978-3-13-139554-2 , p. 129.
  • Otto Henker: Introduction to the theory of glasses . SEVERUS Verlag, 2011, ISBN 978-3-86347-026-5 . , Reprint of the original edition from 1921, pp. 87ff.
  • Anselm Kampik, Franz Grehn, Elisabeth M. Messmer: Specialist examination in ophthalmology. 1000 commented exam questions. Thieme, Stuttgart et al. 2006, ISBN 3-13-142131-2 , p. 189.