In vitro strehl ratios with spherical, aberration-free, average, and customized spherical aberration-correcting intraocular lenses.

PURPOSE: To determine in vitro image qualities of artificial eyes achieved with spherical, aberration-free, average spherical aberration-correcting, and customized spherical aberration-correcting IOLs in centered, decentered, and tilted positions.

METHODS

The in vitro performance of these IOL models was determined by optical bench measurements. The experimental setup included a laser light source controlled by aperture stops that corresponded to 3- and 5-mm pupil apertures, an artificial eye with three alternative corneal models exhibiting low, intermediate, and high spherical aberration (SA), IOLs mounted to an immersed IOL holder that could be moved laterally and tilted, and a charge-coupled device camera and software to determine three-dimensional point spread function (PSF), modulation transfer function, and Strehl ratio.

RESULTS

Differences among the various lens models turned out to be low for a 3-mm pupil. For a pupil aperture of 5 mm, customized IOLs showed the best results for perfect lens positioning. With ongoing decentration and tilt, customized IOLs rapidly lost their advantages, particularly in corneas with high SA and IOLs of high diopters. Spherical IOLs were always inferior to aberration-free IOLs.

CONCLUSIONS

Reasonably well-centered aberration-correcting IOLs may provide considerably better image quality than conventional spherical IOLs. In the presence of significant postoperative decentration and tilt of the IOL, aberration-free IOLs are the safest option among the various intraocular lens designs.