The Collaborative International Dictionary of English v.0.48:

Tonometry \To*nom"e*try\, n.
   The act of measuring with a tonometer; specifically (Med.),
   measurement of tension, esp. the tension of the eyeball.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tonometry
    n 1: the measurement of intraocular pressure by determining the
         amount of force needed to make a slight indentation in the
         cornea