distometer

distometer

An instrument for measuring the distance between the back surface of a spectacle lens and the apex of the cornea. It is usually carried out by having the patient close the eyes. One end of the instrument or caliper rests against the upper eyelid and the other presses against the back surface of the spectacle lens. The measurements are most commonly given to the nearest 0.5 mm. Syn. Lenscorometer (a tradename); vertexometer.