Fourier Tools for the Evaluation of Refractive Multifocal Designs

Abstract

Tools and methods for the theoretical evaluation of optical properties of refractive multifocal commercial designs are presented, which use segmentation techniques to divide the pupil and classical Fourier optics. They can be applied to refractive designs such as multifocal contact lenses and intraocular lenses as well as to the study of small aperture designs and corneal inlays. In this paper, the optical profiles of 12 multifocal, commercially available, contact lenses from four companies were measured with the help of the NIMO equipment (LAMBDA-X). The corresponding through-focus Visual Strehl ratios were computed in the frequency domain to quantify image quality as a single scalar value. The multifocal properties of each of the commercial contact lenses were evaluated for three different base prescriptions (-6.00 D, -3.00 D, and + 1.00 D) in 65 patients. The contact lenses of this study were also evaluated in conjunction with the higher-order aberrations obtained from 65 eyes collected by using a standard Shack-Hartmann sensor. The diameters used for the evaluation of the contact lenses varied according to each eye’s pupil size (from 2.45 to 6.27 mm). The proposed tools have allowed us to evaluate multifocal solutions in a theoretical manner without the necessity of creating prototypes. They helped us differentiate between lenses created for young and old presbyopes, instructed the proper utilization of hyperfocal distance in the field of contact lens design, and demonstrated the importance of the effective aperture effect. This is the first proposed method that converts sagittal powers of multifocal solutions into their equivalent optical quality metric. It can be applied to the evaluation of myopia control methods. It is the author’s hope that the reader appreciates the tools presented and uses them to further the field of refractive multifocality.