Autorefractor

Automatic glasses prescription estimation

Overview

An autorefractor is a computer controlled instrument that objectively measures the refractive error of the eye, estimating the sphere, cylinder, and axis of the correcting lens. Most use infrared light projected into the eye and analyze the light reflected from the retina, while the eye views a target designed to relax accommodation. Measurements take seconds and require no responses, making them useful for screening, for children, and as a starting point for a full refraction. Retinoscopy is the traditional manual equivalent, in which the examiner observes the reflex of a streak of light in the pupil while introducing lenses. Autorefraction is usually refined by subjective refraction, in which lenses are changed in a phoropter or trial frame while the patient compares options, because the most comfortable prescription depends on perception and visual needs. Cycloplegic drops are often used in children to prevent accommodation from masking hyperopia. Wavefront aberrometers extend objective measurement to higher order aberrations and are used in planning customized laser refractive surgery.