Source : Webster's Revised Unabridged Dictionary (1913)

Astigmatic \As`tig*mat"ic\, a. (Med. & Opt.)
   Affected with, or pertaining to, astigmatism; as, astigmatic
   eyes; also, remedying astigmatism; as, astigmatic lenses.

Source : WordNet®

astigmatic
     adj : of or relating to a defect in the eye or in a lens caused by
           a deviation from spherical curvature which prevents
           light rays from meeting at a common focus and so
           results in distorted images [ant: {anastigmatic}]