astig·ma·tism /əˈstɪgməˌtɪzəm/
 散光


 astig·ma·tism /əˈstɪgməˌtɪzəm/ 名詞
 散光


 A·stig·ma·tism n.  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.

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 astigmatism
      n 1: (ophthalmology) impaired eyesight resulting usually from
           irregular conformation of the cornea [syn: 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: astigmia] [ant: stigmatism]