OPSIOMETER
Etymology
Noun
opsiometer (plural opsiometers)
An old instrument for measuring vision and determining the focal length of a lens that can correct an individual's imperfect eyesight.
Anagrams
• opisometer
Source: Wiktionary
Op`si*om"e*ter, n. Etym: [Gr. -meter: cf. F. opsiomètre.]
Definition: An instrument for measuring the limits of distincts vision in
different individuals, and thus determiming the proper focal length
of a lens for correcting imperfect sight. Brande & C.
Source: Webster’s Unabridged Dictionary 1913 Edition