Background.Correction of infant aphakia with conventional soft and rigid designs induces significant amounts of positive spherical aberration.Methods.Different levels of positive spherical aberration were induced by rigid lenses positioned close to the eye. Visual acuity and depth of focus were measured for twelve young adult subjects.Results.Positive spherical aberration acts to produce an increase in relative depth of focus, but because of the reduction of best visual acuity, there is a concurrent decrease in absolute depth of focus. As the spherical aberration increases, there is a progressive loss of best-corrected visual acuity.Conclusions.The correction of spherical aberration in contact lenses for infant aphakia provides the best theoretical optical conditions for normal ocular growth and visual development. We provide examples of the optimal aspheric surfaces to minimize spherical aberration in contact lenses for infant aphakes.