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 [syn: diopter, dioptre]
Dioptre \Di*op"tre\, n. [F. See 2d Dioptric.] (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.
[1913 Webster]
