The Collaborative International Dictionary of English v.0.48:

Emmetropia \Em`me*tro"pi*a\ ([e^]m"m[-e]*tr[=o]"p[i^]*[.a]), n.
   [NL., fr. Gr. 'e`mmetros in measure, proportioned, suitable
   ('en in + me`tron measure) + 'w`ps, 'wpo`s, eye.] (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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

emmetropia
    n 1: (ophthalmology) the normal refractive condition of the eye
         in which there is clear focus of light on the retina