"measurement of the range of vision; measurement of the visual powers in general," 1886, from optometer (1738), name given to an instrument for testing vision, from opto- "sight," from Greek optos "seen, visible" (from PIE root *okw- "to see") + -metry "a measuring of." Probably influenced by French optométrie.
When I made the foregoing Experiments, I designed to repeat them with more Care and Exactness, and to make some new ones of the same Sort, by means of an Instrument I had contrived for that Purpose; which from its Use in measuring the Limits of distinct Vision, and in determining with great Exactness the Strength and Weakness of Sight, may be called an Optometer. [Dr. William Porterfield, "An Essay Concerning the Motions of our Eyes, Part II," in Medical Essays and Observations, Vol. IV, Edinburgh, 1738]