Focométrie

A focometer is an instrument that measures refractive errors and is intended to provide spherical eyeglass prescriptions to rural or economically disadvantaged populations without the need for complicated protocols, expensive equipment, or electricity. The focometer is monocular and hand-held, and is normally used in natural lighting. Patients rotate a collar on the focometer until the best focus is achieved. The individual's refractive power is then read off a linear dioptre scale.