dioptry

noun

1. (alt-of, alternative, obsolete)Alternative form of diopter.

   “The Dioptral System of numbering prisms alone possesses the great desideratum of establishing a direct and simple relation between the prism-dioptry and the lens-dioptry, as demonstrated by the authors' law, that "a lens decentered one centimeter will produce as many prism-dioptry as the lens has dioptry of refraction."”

   “They also shared a fearful myopia of identical dioptry, were apt to bump into inanimate objects, sit down on invisible chairs, or bounce off each other as they shambled about talking and gesticulating.”