\Di*op"tric\, a. (Optics)
Of or pertaining to the dioptre, or to the metric system of
numbering glasses. -- n. A dioptre. See {Dioptre}.

\Di*op"tric\, Dioptrical \Di*op"tric*al\, a. [Gr. ?
belonging to the use of the ?; ? = dia` through + the root of
? I shall see: cf. F. dioptrique.]
Of or pertaining to dioptrics; assisting vision by means of
the refraction of light; refractive; as, the dioptric system;
a dioptric glass or telescope. ``Dioptrical principles.''
--Nichol.
{Dioptric curve} (Geom.), a Cartesian oval. See under
   {Cartesian}.