Vanishing optotypes and objective measurement of human visual acuity

Abstract

The eye resolving power and human visual acuity are the most important parameters of physiological optics. In this study, we compare our results of psychophysics, subjective measurement of visual acuity, with the results of electrophysiological measurement, objective measurement of visual acuity using vanishing optotypes that differ in spatial (sharp or non-sharp) and semantic (animate or inanimate) properties. The subject is instructed to provide consciously the classification of images: are they sharp, or are they non-sharp. At the same time the subject unconsciously provides another classification: what objects presented to him as images are animate or inanimate. This unconscious classification was provided by the subject without instruction to do it, and it was independent of his conscious decisions made during testing of the presented images of the objects (sharp or non-sharp). We see the observer’s unconscious classification (animate or inanimate) only using electrophysiological measurements. The markers of unconscious recognition are the visual evoked potential components P200 and N170, recorded from the frontal brain area. The discovered effect works as an instrument for objective visual acuity measurements.