System for measurement of refractive error of an eye based on subjective distance metering

An apparatus for providing an indication of at least one refractive error of a subject's eye, the apparatus comprising: means for displaying at least one target image on a display area; at least one processor comprising means for receiving feedback from the subject for each displayed target image indicating that the subject is located at a maximum distance of best acuity, MDBA, from the target image among multiple distances experienced by the subject when viewing the image objective image with one eye of the same, said MDBA being the maximum distance at which said subject clearly recognizes one or more visual elements of said target image using said eye; at least one sensor for acquiring data representing an actual distance between the subject's eye and said target image corresponding to the subjective MDBA; the at least one processor further comprising a distance estimation and calibration module (112) to estimate the MDBA according to said acquired data, and a feedback module (113), and which is configured to calculate at least one parameter associated with the error of refraction of the eye, the at least one calculated parameter is based on said target image and the estimated MDBA.