SG Heritage Dictionary

Dioptrical [\N] Webster's Dictionary 1828

1. DIOPTRIC, DIOPTRICAL adjective [Gr., to see through; to see.]

2. Affording a medium for the sight; assisting the sight in the view of distant objects; as a dioptric glass.

3. Pertaining to dioptrics, or the science of refracted light.

Dioptrical [Adjective] Webster's Dictionary 1913

Of or pertaining to dioptrics; assisting vision by means of the refraction of light; refractive; as, the dioptric system; a dioptric glass or telescope.