astigmatism
n 1: (ophthalmology) impaired eyesight resulting usually from
irregular conformation of the cornea; common in nearsighted
people [syn: {astigmatism}, {astigmia}]
2: (optics) defect in an optical system in which light rays from
a single point fail to converge in a single focal point [syn:
{astigmatism}, {astigmia}] [ant: {stigmatism}]
ametropia \am`e*tro"pi*a\ ([a^]m`[-e]*tr[=o]"p[i^]*[.a]), n.
[Gr. 'a`metros irregular + 'w`ps, 'wpo`s, eye.] (Med.)
A visual impairment resulting from faulty refraction of light
rays in the eye. Subtypes include {myopia} {astigmatism} and
{hyperopia}. -- {Am`e*trop"ic} ([a^]m`[-e]*tr[o^]p"[i^]k), a.
AS
[1913 Webster +PJC]
Astigmatism \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.
[1913 Webster]
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.
[1913 Webster]