The theoretical effect of intraocular lens shape on on-axis performance of model pseudophakic eyes was investigated. Image quality criteria included the magnitude of spherical aberration (both wave and longitudinal), spot diagrams, and the modulation transfer function. For eyes with corneal asphericities encompassing most of the population (Q greater than or equal to -0.5), the optimum lens form is close to being plano-convex, with the more curved surface facing the cornea.