Presbyopia

Webster's Dictionary

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.

The Nuttall Encyclopedia

Diminution of sight due to age, occurring usually about forty-five, when near objects are less distinctly seen than distant, an affliction due to the flattening of the lens.