Residual fit error of multifocal contact lenses as a function of increasing Zernike coefficients

Abstract

Purpose : Complex optical designs such as multifocal lenses are being utilized for myopia control. Zernike polynomials are used to calculate metrics of image quality to predict visual performance. We determined if Zernike polynomials can adequately fit zonally reconstructed wavefront maps of multifocal contact lenses.

Methods : Three center-distance multifocal lenses (Biofinity “D” +2.50 add, Proclear “D” +2.50 add, NaturalVue) were studied. The Biofinity and Proclear lenses have a gradual radial increase in plus power from the lens center, while the NaturalVue Multifocal has an extended depth of focus design. Two lenses of each power ranging from -1.00 to -6.00D in 1D steps were measured for each lens design. Wavefront aberrations of each lens were measured in a wet cell with the SHSOphthalmic aberrometer and used to reconstruct zonal wavefront error maps. The wavefront error maps were then fitted with Zernike polynomials through the 6^th, 7^th, 10^th, 15^th, 20^th, 25^th and 30^th radial orders for a 6mm diameter pupil. The accuracy of each Zernike fit was calculated as the root-mean-square (in microns) of the difference between the zonal wavefront error map and the modal wavefront error map reconstructed from each Zernike fit. A repeated-measures ANOVA was used to determine the effect of lens design and Zernike radial order on the residual fit error.

Results : Root-mean-square of the residual fit error wavefront map (RMSFE) depended on both the lens design and radial order of the Zernike fit (lens x order interaction; p < 0.0001). RMSFE decreased for all three lenses with increasing radial order. For a 6^th order fit, RMSFE was less than 0.1µm for the Biofinity and Proclear lenses and 0.22µm for the NaturalVue. RMSFE reduced to less than 0.05 µm for all three lenses with the 15^th order polynomial fit. There was little additional improvement in the RMSFE (< 0.005µm) between the 20^th and 30^th order fits for both Biofinity and Proclear, but there was an additional 0.014µm reduction in RMSFE for the NaturalVue design. There was no difference in RMSFE between all three lens designs with the 30^th order fit.

Conclusions : Zernike fits were able to describe the multifocal optics of the lenses studied, but the number of radial orders needed depended on the complexity of the multifocal lens design, requiring through the 25^th radial order for one design.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.