We determined the influence of adaptive optics correction on through-focus illiterate-E visual acuity and through-focus contrast sensitivity under monochromatic conditions. In two subjects, adaptive optics improved high and low (12%) contrast in-focus visual acuity by 0.1 to 0.15logMAR, but resulted in more rapid and more symmetrical deterioration in visual acuity away from in-focus. In one subject, adaptive optics improved in-focus contrast sensitivity and resulted in more symmetrical and greater loss of contrast sensitivity about the peak sensitivity because of correction of higher-order aberrations. The results show that full correction of higher-order aberrations may worsen spatial visual performance in the presence of some defocus.