The invention is about a human identification method based on the perception of low-intensity light. In its path towards the retina, light suffers optical losses. For any illuminated ganglion receptive field, the number of detected photons divided by the number of photons incident on the eye is called a, and is different from field to field for the same subject, and for geometrically similar fields in different subjects. The identification is based on a a-map. The user is asked to respond positively/negatively on the perception of light pulses illuminating various receptive fields chosen to have either high-α or low-α. The choice is random, hence an impostor is forced to respond randomly to the device's interrogations. The illumination of receptive fields can be done serially or in parallel, leading quickly to false positive and false negative identification probabilities at the level of 10−10 and 10−4, respectively.