n. 散光

[化] 像散

[医] 散光

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.

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.

Ametropia \Am`e*tro"pi*a\, n. [Gr. ? irregular + ?, ?, 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.
[1913 Webster +PJC]