Biconcave freeform implantable contact lenses: wide-field design and peripheral aberration optimization

We propose a wide-field biconcave implantable contact lens (ICL) design framework that combines third-order Seidel aberration theory with a field-dependent double Zernike (DZ) freeform surface model to address off-axis aberration growth and peripheral image-quality degradation under wide-field conditions. A wavefront model for the biconcave structure is established, and a full-field weighted RMS metric is introduced to evaluate global optical performance over the 0°-20° half-field range. Simulations based on the Liou-Brennan eye model show that the proposed biconcave ICL maintains superior off-axis MTF at large field angles compared with plano-concave and meniscus baselines under both -2.00 D and -5.00 D correction conditions. In terms of the full-field RMS metric, the biconcave design performs best in the -2.00 D case, while the meniscus design yields the lowest integrated RMS in the -5.00 D case. These results indicate that the proposed biconcave freeform design is particularly advantageous for peripheral wide-field image-quality preservation, while its global wavefront advantage depends on the correction level.