Low contrast visual acuity in pseudophakic patients implanted with an anterior surface modified prolate intraocular lens

Purpose: To determine whether implantation of a new intraocular lens (IOL) with a modified prolate anterior surface, designed to reduce the positive spherical aberration of the pseudophakic eyes, results in improved contrast sensitivity assessed in terms of low contrast visual acuity (VA). Methods: We carried out an intraindividual study of 12 patients with bilateral cataracts, randomized to receive a prolate anterior surface IOL (Tecnis Z9000, Pharmacia) in one eye and a biconvex spherical surface IOL (CeeOn 911 A, Pharmacia) in the other. High and low contrast VA was assessed under photopic conditions, before and after pupil dilation. Results: After mydriasis, the Technis Z9000 provided significantly better low contrast VA at contrast levels £ 25%. No significant difference was found under normal pupil conditions. Conclusion: Our results confirm the hypothesis that the spherical aberration of the eye after cataract surgery can be reduced by an anterior prolate surface IOL.