1. A non-transitory storage media comprising computer-executable instructions operable to, when executed by at least one computer processor, enable the at least one computer processor to implement one or more operations of providing an indication of at least one refractive error of an eye of a subject, said operations comprising: triggering a displaying of at least one selected dynamic or fixed target image over a display area; for each displayed target image, receiving subjective feedback from the subject indicating that the subject is positioned at a maximum distance of best acuity (MDBA) from the target image out of multiple distances experienced by the subject when viewing the target image with one eye thereof, said MDBA being the maximum distance in which the subject clearly recognizes at least one sign or visual effect of said target image; triggering an acquiring of data associated with a distance between the tested eye of the subject and the target image, at least when the subject has reached the MDBA, using at least one sensor; triggering an estimating of the MDBA according to said acquired data; and triggering a calculating of at least one parameter associated with the refractive error of the tested eye according to the estimated MDBA and according to characteristics of the displayed at least one target image, using at least one processor.