Imaging Quality of Bifocal Piggyback Intraocular Lens versus ReSTOR and TECNIS Multifocal Lenses

Purpose The imaging quality provided by a piggyback integrated by a monofocal intraocular lens (IOL) + a bifocal IOL of zero power and +3.75 diopters of addition is compared with the optics quality of a simple multifocal IOL of the same power and addition. Methods The imaging quality was evaluated by determining the modulation transfer function (MTF), using an artificial eye simulating in vivo conditions of the anterior chamber, including an artificial cornea and a wet cell containing physiologic solution where the IOL was positioned. The MTFs of the bifocal piggyback for near and distance vision were measured, with pupil diameters of 3 and 5 mm, and compared with the MTFs of an equivalent power of ReSTOR and TECNIS multifocal IOLs measured under the same conditions. Results The MTFs for distance and near focus of the bifocal piggyback are similar to the MTFs of the ReSTOR and TECNIS multifocal IOLs with the two diameters of pupil. A more accurate comparison, values of average modulation, and Strehl ratio show a greater similitude with ReSTOR than with TECNIS. Conclusions The bifocal piggyback system provides a similar imaging quality to that obtained with a ReSTOR multifocal IOL and, like the ReSTOR, provides better performance in distance vision than in near vision, whereas the TECNIS multifocal IOL provides the best performance.