The Collaborative International Dictionary of English v.0.48:

Presbyopia \Pres`by*o"pi*a\[NL., from Gr. ? old, n., an old man
   + ?, ?, the eye.] (Med.)
   A defect of vision consequent upon advancing age. It is due
   to rigidity of the crystalline lens, which produces
   difficulty of accommodation and recession of the near point
   of vision, so that objects very near the eyes can not be seen
   distinctly without the use of convex glasses. Called also
   presbytia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

presbyopia
    n 1: a reduced ability to focus on near objects caused by loss
         of elasticity of the crystalline lens after age 45 [syn:
         presbyopia, farsightedness]