A keratometer is an instrument used to measure the curvature of the cornea. Synonyms for keratometer include corneal topographer, ophthalmic topographer, and corneal mapping system. These different names refer to slightly different technologies and applications, but they all share the same goal of mapping the surface of the cornea to aid in diagnosing and treating eye conditions such as astigmatism, corneal dystrophy, and keratoconus. Other related terms include optical biometer, which measures additional dimensions of the eye such as length and depth, and autokeratometer, which is a type of keratometer that uses infrared light to measure the cornea's curvature.