An Auto refractometer, also known as an automated refractometer, is a computer-controlled machine that measures a person's refractive error and generates a prescription for glasses or contact lenses during an eye examination. This is accomplished by observing how light changes when it enters the eye of a person. By measuring how light is altered as it reflects through the eyeball, an autorefractor is used to estimate an individual's contact. For the patient, the procedure is quick and painless, and the data provides a baseline from which to calculate the proper eyeglass or contact lens prescription. Keratometers are now integrated with autorefractometers commonly known as Autorefractor Keratometer used to measure corneal curvature. corneal curvature determines the power of the cornea.