Abstract: Visual acuity of a subject is ascertained by displaying to the subject sets of symbols having a different size, recording the subject's responses identifying each symbol, calculating a rate of recognition for each symbol size, and determining the client's visual activity based on the rate of recognition.

Abstract: The invention relates to a method for measuring visual acuity of a subject, said method comprising the steps of providing a set of optotypes, providing a pre-calculated value of similarity for pairs of optotypes selected from the set of optotypes, displaying to the subject sub-sets of optotypes of the set of optotypes in different optotype size, receiving for each displayed optotype of one of said sub-set of optotypes of a given optotype size a response of the subject indicative of an optotype (identified optotype) selected from the set of optotypes, registering for each response a value of similarity corresponding to the pre-calculated value of similarity of the pair of optotypes consisting of the displayed optotype and the identified optotype indicated in the response, calculating a value of rate of recognition for each optotype size, the value of rate of recognition for a given optotype size being an average of the registered values of similarity for the responses to the optotypes displayed in the given

Abstract: In clinical visual acuity measurements a method a system and a device for measuring visual acuity of a client is provided. In accordance with the implementation, the system comprises a display device (41), an input device (42) and a computing device (43). The display device (41) is capable of displaying sets of symbols in different size to the client. The input device (42) is capable of receiving responses of the client indicative to the identity of the symbols, and the computing device (43) is capable of a) registering (S431) values to the responses belonging to pre-calculated values of similarity of the symbols, b) calculating (S432) a rate of recognition value for each symbol size, and c) determining (S433) the measured visual acuity from the rate of recognition values.