emmetropia
  正常眼
  em·me·tro·pia /ˌɛməˈtropɪə/ 名詞
  屈光正常,正視眼(正常視力)
  Em·me·tro·pi·a n.  Med. That refractive condition of the eye in which the rays of light are all brought accurately and without undue effort to a focus upon the retina; -- opposed to hypermetropia, myopia, and astigmatism.
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  emmetropia
       n : (ophthalmology) the normal refractive condition of the eye
           in which there is clear focus of light on the retina