In 2017, nation-wide vision screening tests under the name of "Wzrok na 6" have been carried out with oversight of the National Public Health Institute and with partnership of the Faculty of Physics at the University of Warsaw. 451 children of early school age were examined. The aim of the paper was to analyze the results of cover test and visual acuity test to find interdependence. Statistically significant correlations have been found between these tests, in the distinction between correct and abnormal results of individual tests.