The Collaborative International Dictionary of English v.0.48:

Nearsightedness \Near"sight`ed*ness\, n. (Med.)
   An eyesight abnormality resulting from the eye's faulty
   refractive ability, such that one can see only close objects
   distinctly; the condition of being nearsighted. See Myopic,
   and Myopia.

   Syn: myopia, shortsightedness.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

nearsightedness
    n 1: (ophthalmology) eyesight abnormality resulting from the
         eye's faulty refractive ability; distant objects appear
         blurred [syn: myopia, nearsightedness,
         shortsightedness] [ant: farsightedness,
         hypermetropia, hypermetropy, hyperopia,
         longsightedness]