An ophthalmic device intended to be placed in front of a patient's eyes to measure the refractive error of the eye (the inaccuracies of focusing light upon the retina) during an ophthalmic examination, typically to determine a patient's prescription for glasses. It typically consists of two mounted, disk-like housings which contain lenses of different characteristics. It is designed such that the optometrist can change the lenses and other settings while asking the patient to read an eye chart and to provide subjective feedback on which settings give best vision. The setting changes may be manual or automated.