astigmatism : Dictionary / Wörterbuch (BEOLINGUS, TU Chemnitz)

English Dictionary: astigmatism	by the DICT Development Group
2 results for astigmatism
From WordNet (r) 3.0 (2006) [wn]:
astigmatism n (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people Synonym(s): astigmatism, astigmia (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point Synonym(s): astigmatism, astigmia Antonym(s): stigmatism
From Webster's Revised Unabridged Dictionary (1913) [web1913]:
Astigmatism \Astig"matism\, n. [Gr. 'a priv. + [?], [?], a prick of a pointed instrument, a spot, fr. [?] to prick: cf. F. astigmatisme.] (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 indistinctness of vision. Note: 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.