opsiometer


From The Collaborative International Dictionary of English v.0.48:

Opsiometer \Op`si*om"e*ter\, n. [Gr. ? sight + -meter: cf. F.
   opsiom[`e]tre.]
   An instrument for measuring the limits of distinct vision in
   different individuals, and thus determiming the proper focal
   length of a lens for correcting imperfect sight. --Brande &
   C.
   [1913 Webster]
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