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Noun: diopter  dI'óp-tu(r)
  1. 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
    "Her new glasses had a prescription of +2.5 diopters";
    - dioptre [Brit, Cdn]

Derived forms: diopters

Type of: unit, unit of measurement

Encyclopedia: Diopter