Source : Webster's Revised Unabridged Dictionary (1913)

Ophthalmometer \Oph`thal*mom"e*ter\, n. [Gr. ? eye + -meter.]
   (Physiol.)
   An instrument devised by Helmholtz for measuring the size of
   a reflected image on the convex surface of the cornea and
   lens of the eye, by which their curvature can be ascertained.