Keratometers

Part of speech: noun

Definitions

1. An instrument used to measure the curvature of the cornea in the eye
2. A device that helps in determining refractive errors by analyzing corneal surface shape
3. An optical tool employed in ophthalmology to assess the shape and topography of the cornea for diagnostic purposes

Etymology: "Keratometers" is the plural of "keratometer", so it names the instrument itself, and the word is built from two Greek elements. The first, "kerato-", comes from Greek "keras", meaning horn, and it appears in English medical terms because the cornea, the transparent front surface of the eye, was compared to horn in its hardness and translucence. The second, "-meter", comes from Greek "metron", meaning measure, and is the same ending found in thermometer or barometer. Put together, the word describes a device for measuring the curvature of the cornea. Like most instrument names of this kind, it is a technical coinage assembled from classical roots rather than a term the ancient Greeks themselves used for an eye instrument.