dioptre Meaning, Definition & Usage

  1. noun a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists
    diopter.

WordNet

Di*op"tre noun
Etymology
F. See 2d Dioptric.
Definitions
  1. (Optics) A unit employed by oculists in numbering glasses according to the metric system; a refractive power equal to that of a glass whose principal focal distance is one meter.

Webster 1913