Optometer

Part of speech: noun

Pronunciation: /ɑpˈtɑmətəɹ/

Definitions

1. A device designed for measuring refractive errors in vision helps determine visual acuity and the ideal corrective lens prescriptions needed for optimal sight
2. This instrument functions to assess the clarity of vision and evaluates necessary optical corrections by measuring refractive discrepancy
3. A tool used to evaluate the eye's focusing ability to identify prescription needs for glasses or contact lenses

Etymology: "Optometer" is a compound built from two Greek-derived elements: "opto-", from Greek "optos" meaning "seen" or "visible" (related to the verb "optesthai," "to see"), and "-meter," from Greek "metron," meaning "measure." Put together, the word names an instrument for measuring the eye's power of sight, which is exactly what it still means. The more interesting part is the word's sibling. "Optometrist" and "optometry" are the familiar forms today, and the "-metrist" and "-metry" endings grew out of the same measuring element. Modern English keeps "optometer" as the name of the device itself, though in everyday use it has largely been overtaken by the professional terms.