Keratometer

Part of speech: noun

Definitions

1. An instrument that quantifies the corneal curvature and surface characteristics is used in ophthalmology for evaluating visual health
2. A device designed to assess the shape and curvature of the eye's cornea for medical examination
3. An ophthalmic tool that measures the corneal surface contour to assist in vision diagnosis

Etymology: The keratometer is a fairly transparent piece of scientific vocabulary: it combines "kerato-", from the Greek "keras" meaning "horn", with "-meter", from the Greek "metron" meaning "measure". The horn in question is the cornea, the clear dome covering the front of the eye. Early anatomists compared its hard, transparent quality to horn, and the same Greek root gives "keratin" and "keratosis", so the word is built from a stem that medical writers used for many tissues with a tough or horny texture. The instrument itself measures how steeply the cornea curves, which determines much of the eye's focusing power and is central to fitting contact lenses and planning cataract or refractive surgery. Because it is a modern device, the word was coined from classical roots to name it, not borrowed from ancient Greek usage, which had no such instrument to describe.