This paper reviews the optics of higher-order and spherical aberrations and discusses aspheric intraocular lenses, attempting to address 2 questions that, despite an abundance of information, remain unanswered: what amount of ocular spherical aberration has been correlated with optimum visual performance, and for what final amount of spherical aberration should the cataract surgeon aim? Finally, the paper briefly reviews recent publications and makes suggestions for future studies in the area.