An Etymological Dictionary of Astronomy and Astrophysics

Any of various instruments for measuring refractive errors of the eye.

Etymology (EN): From opto- “vision; eye; optis,” combining form from Gk. optos “seen, visible,” from opsesthai “be going to see,” related to ops “eye;” → -meter.

Etymology (PE): Did, → vision; -sanj, → -meter.