Source : Webster's Revised Unabridged Dictionary (1913)

Dioptric \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}.