Optical quality testing of monofocal intraocular lens implants with a 3 mm and a 4 mm aperture

The optical quality of 81 monofocal poly(methyl methacrylate) intraocular lenses (IOLs) from eight U.S. firms was tested using a 3 mm aperture, as recommended by the American National Standards Institute Z80.7 standard for IOLs, and a 4 mm aperture. The use of the larger aperture had no effect on the measurements of refractive power and astigmatism. When examined with the 3 mm aperture, the average resolving power of the IOLs was 81% of the diffraction limit; when examined with the 4 mm aperture, the average resolving power was 67% of the diffraction limit. Use of the larger aperture would ensure that a larger area of the IOL had been examined. Incorporating the larger aperture into the ANSI minimum resolution requirement would not appreciably affect the rejection rate for currently manufactured monofocal lenses.