astigmatism Meaning, Definition & Usage
-
noun (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people
astigmia.
-
noun (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point
astigmia.
WordNet
A*stig"ma*tism noun
Etymology
Gr. priv. + , , a prick of a pointed instrument, a spot, fr. to prick: cf. F.Definitions
(Med. & Opt.) A defect of the eye or of a lens, in consequence of which the rays derived from one point are not brought to a single focal point, thus causing imperfect images or indistictness of vision. ✍ The term is applied especially to the defect causing images of lines having a certain direction to be indistinct, or imperfectly seen, while those of lines transverse to the former are distinct, or clearly seen.
