The low-order aberration leading to better visual acuity is calculated from the results of measurement of an eye characteristic by an eye characteristic measuring instrument that can measure up to the high-order aberration, and data on a correction factor is collected, thereby obtaining a result more approximate to the subjective value. According to at least measurement data representing the wave aberration of the eye being examined (S 401 , S 403 ), an image data creating unit creates optotype retina image data by conducting simulation of the visual acuity of an optotype (S 405 ), considering the correction factor for refraction correction. A correction factor setting unit sets a correction factor to be given to the image data creating unit (S 417 ). A judging unit judges from the correction opotype retina image data corrected by the correction factor whether or not an adequate correction factor is set (S 407 to S 421 ). The correction factor setting unit sets a correction factor on the basis of the results of judgment by the judging unit, and changes the correction factor until the judging unit judge that the correction factor is adequate.
Correction-factor determination apparatus and method