Opsiometer

• (n.) 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.
Found on http://thinkexist.com/dictionary/meaning/opsiometer/

Opsiometer

Op`si·om'e·ter noun [ Greek ... sight + -meter : confer French opsiomètre .] 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.
Found on http://www.encyclo.co.uk/webster/O/26

opsiometer

instrument for testing vision
Found on http://phrontistery.info/o.html
No exact match found