The Collaborative International Dictionary of English v.0.48:

Long-sightedness \Long"-sight`ed*ness\, n.
   1. The state or condition of being long-sighted; hence,
      sagacity; shrewdness.
      [1913 Webster]

   2. (Med.) See Hypermetropia.
      [1913 Webster]

WordNet (r) 3.0 (2006):

longsightedness
    n 1: abnormal condition in which vision for distant objects is
         better than for near objects [syn: hyperopia,
         hypermetropia, hypermetropy, farsightedness,
         longsightedness] [ant: myopia, nearsightedness,
         shortsightedness]