Source : Webster's Revised Unabridged Dictionary (1913)

Optometry \Op*tom"e*try\, n.
   1. (Med.) Measurement of the range of vision, esp. by means
      of the optometer.

   2. As defined (with minor variations) in the statutes of
      various States of the United States:
      (a) ``The employment of subjective and objective
          mechanical means to determine the accomodative and
          refractive states of the eye and the scope of its
          function in general.''
      (b) ``The employment of any means, other than the use of
          drugs, for the measurement of the powers of vision and
          adaptation of lenses for the aid thereof.''

Source : WordNet®

optometry
     n : the practice of an optometrist