Definitions for: Astigmatism


[n] (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point
[n] (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea



Webster (1913) Definition: A*stig"ma*tism, 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.

Synonyms: astigmia

Antonyms: stigmatism

See Also: ametropia, condition, keratectasia, keratoconus, status

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