Studies have demonstrated a nearly linear decline in image quality with age, suggesting a significant increase in the optical aberrations in the eye over time. 8-9 Advances in wavefront technology have opened a new door to the measurement of ocular aberrations. 9-10 Also, this technology allowed the development of a new type of IOL designed to compensate for the positive spherical aberration of the cornea, which is one of the most important aberrations contributing to visual deterioration of the pseudophakic eye. 11-14 Based on these findings, the approach to compensate for increasing spherical aberration in older eyes is to develop an IOL that introduces negative spherical aberration into the system. Such an IOL, the Tecnis Z9001® IOL (Model Z9001, Advanced Medical Optics, Santa Ana, CA), has been developed by AMO. This is a polysiloxane foldable 3-piece IOL, with anterior aspheric surface (negative spherical aberration) designed to decrease the total amount of ocular spherical aberration after cataract surgery.7