The Humphrey Vision Analyzer tm: reliability and validity of refractive-error measures.

Four subjective measures of the refractive error of 42 eyes (21 patients) were obtained by 2 examiners, one using a Humphrey Vision Analyzer TM and the other using a conventional refractor. Each examiner made 2 separate measures of each subject's refractive error, one without and one with an added cylindrical lens chosen at random from a predetermined set of powers and axes. The order of using the instruments and the added lenses was mixed. Measures of the refractive errors differed with the 2 instruments by approximately the same amount on average as did duplicate measures with either instrument. Refractive-error measures obtained with the 2 instruments are about as valid as they are repeatable.