Wavefront measurements of diffractive and refractive multifocal intraocular lenses in an artificial eye

PURPOSE: To investigate whether wavefront measurements taken in eyes that have implanted multifocal intraocular lenses (IOLs) are reliable when creating laser refractive surgical treatments to remove residual refractive error from these eyes. METHODS: A specially designed fluid-filled model eye holding a multifocal IOL was refracted using a commercial wavefront eye refractor. The wavefront findings were then compared to the expected refractive error. The fluid-filled model was designed to match the optical characteristics of a human eye and to hold the IOL at the same distance from the cornea as in a human eye. Lenses tested were AMO Tecnis ZM900 series (diffractive design, +25.00 D, +4.00 D add), AMO ReZoom NXG1 series (refractive design, 25.00 D, +4.00 D add), and AMO 811E (diffractive with aspheric design 25.00 D, +4.00 add). The visible pupil diameter was 5.75 mm. RESULTS: Diffractive bifocal IOLs were found to create spot doubling in the Shack-Hartmann sensor image as expected from theoretical considerations. However, the residual sphere power and cylinder power reported were those expected. In addition, the higher order aberrations reported were reasonable in light of expected results. Refractive multifocal IOLs were found to create distorted Shack-Hartmann images as expected. The residual sphere power and cylinder power reported were not those expected nor were the higher order aberrations. In addition, the higher order values were sensitive to the position of the eye with respect to the refractor. CONCLUSIONS: Wavefront measurements from eyes with diffractive IOLs can be used, with caution, to plan laser refractive treatments. Wavefront measurements from eyes with refractive multifocal IOLs should not be used to plan post-implant laser refractive correction.