An acuity test was developed with defined space between symbols to determine the effect of crowding on visual line acuity. The test differentiates between normalsighted subjects, those with low but uncorrected refractive errors and amblyopes. Furthermore, the test allows a quantitative examination of the crowding phenomenon and a measure of progress during amblyopia therapy. In normal-sighted subjects a maturational effect on visual line acuity was found, reaching the maximum test level at approximately the tenth year of life.