Measuring Defocus Curves of Monofocal, Multifocal and Extended Depth-of-focus Intraocular Lenses Using Optical Bench Test

Purpose: To determine the through-focus optical bench test performance of monofocal, bifocal, and extended depth-of-focus intraocular lenses (IOLs), and to measure their defocus curves. Methods: A model eye was placed on an optical bench to test three different IOLs (TECNIS ZXR00, ZMB00, and ZCB00; Abbott Medical Optics, Santa Ana, CA, USA). The focus was changed by inserting trial lenses from +1.00 diopters to -4.00 diopters, in increments of +0.25 diopters. The 1951 United States Air Force Resolution chart was used to determine the quality of the images. The degree of similarity with reference images was given by the cross-correlation coefficient, and defocus curves were drawn and compared. Results: Bifocal IOLs showed lower image quality with the addition of minus diopter trial lenses, but showed good image quality at near distance. Bifocal IOLs also showed a 'double peak' in their defocus curve. Monofocal IOLs showed a lower image quality and cross-correlation coefficient with addition of lower-diopter trial lenses. The extended depth of focus IOLs showed a single peak in their defocus curve, but had a wider range of diopters and better image quality than monofocal IOLs. Conclusions: Bifocal IOLs showed a double peak defocus curve, and extended depth of focus IOLs showed a wider diopter range and better image quality than monofocal IOLs.