The Handheld Auto Refractometer uses the infrared fundus reflection phase method to emit a beam of infrared light with a specific wavelength, through the subject's cornea, lens, etc., and finally projected to the eye retina, and then reflected back to the corresponding optical system of the instrument. The image is taken through the image sensor, and the spherical refraction power, cylindrical refraction power and astigmatism axis are calculated after image processing and signal processing, which is used to determine the refractive state of human eyes.
An electrically-powered, ophthalmic device designed to be used by a healthcare professional to objectively measure the refractive error of the eye (the inaccuracies of focusing light upon the retina) by measuring how light is changed when it enters the patient's eye(s). The device emits light into the eye and detects the light reflection which is measured for sphere, cylinder, axis and/or high order aberration measurements, typically measured in dioptres (the reciprocal of the focal length of the lens expressed in metres). Also known as an aberrometer, the device uses this information to automatically calculate the lens prescription needed to correct the patient's vision.