Source : Webster's Revised Unabridged Dictionary (1913)

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}.

Source : WordNet®

presbyopia
     n : farsightedness resulting from a reduced ability to focus
         caused by loss of elasticity of the crystalline lens with
         age