This double-blind prospective randomized study included patients with age-related cataract, no indication of existing ocular pathology, unsatisfactory correction with glasses and less than 2.50 diopters (D) of topography cylinder. Patients were offered the opportunity to be part of a clinical trial in which they would be allocated to have cataract surgery with implantation of aspherical or spherical IOL. Patients were randomized to receive a Tecnis Z9001 aspheric IOL in one eye and a ClariFlex spheric IOL in the fellow eye. To protect patient safety, after the first eye surgery, they were asked whether they wished to have the same lens type implanted in the second eye. Written informed consent was obtained from all patients before surgery and the study was approved by the local ethics committee. Exclusion criteria were previous ocular surgery, central endothelial cell count less than 1800 cells/mm2, glaucoma or intraocular pressure greater than 21 mmHg, amblyopic eyes, retinal abnormalities, diabetes mellitus, steroid or immunosuppressive treatment, and connective tissue diseases.