Astigmatism

Astigmatism is a term applied to an eye whose refraction is not thesame in all its parts, causing the eye to focusthe light at different points. It is subdividedinto two kinds, regular and irregular. Irregularastigmatism is where there is a difference ofrefraction in one and the same meridian, andaccording to some authors, is subdivided intonormar ana abnormal.

Source: Ophthalmic Dictionary including pronunciation, derivation and definition of the words used in Optometry and Ophthalmology by James J. Lewis, Oph. D. Professor of Optometry in the Northern Illinois College of Ophthalmology and Otology, Chicago.