It is well known that an important function of binocular vision is to increase the SNR. When a signal simultaneously arrives along two channels, it is summed if the channels are statistically independent. The binocular visual acuity can then theoretically be increased by comparison with the monocular value by a factor of 2, or 1.4. This paper gives the results of experiments to measure the visual acuity by means of Landolt rings. It is established that binocular visual acuity is greater than monocular by a factor of 1.3 on the average. It is assumed that this can be associated with internal multiplicative discretization noise at the level of the retinal receptors. This result is important for understanding image processing in different channels of the visual system.