Freeform extended depth-of-focus intraocular lens for more robust performance against physiological variations

Extended depth-of-focus (EDOF) intraocular lenses (IOLs) aim to provide improved visual performance over a range of distances, but their clinical outcomes are still sensitive to individual biometric variability. Improving the robustness of EDOF IOL optical performance to these patient-specific variations is critical to enhance visual predictability and patient satisfaction following cataract surgery.

We aim to determine if freeform surfaces can improve the robustness of EDOF IOLs by maintaining consistent optical performance (refractive error, depth of field) despite individual biometric variations.

A database of synthetic eyes was adapted to simulate pseudophakic eyes. The post-operative performances (refractive error and depth of field) for three types of EDOF IOLs (L1, L2, L3) were estimated using polychromatic Visual Strehl ratio based on the Optical Transfer Function, with photopic wavelength spectrum for a 3 mm and a 5 mm entrance pupil diameter. L1 is a standard refractive EDOF; L2 is identical to L1 but with a freeform back surface optimized in-eye; L3 is similar to L2 but calculated by a model trained to predict freeform surfaces, using preoperative biometric data (higher-order aberrations of the cornea; effective lens position, calculated from preoperative data; ELP-retina distance; and transverse position of the lens).

The addition of a freeform surface allowed us to significantly reduce the difference between the target refraction and subjective refraction, in polychromatic condition, for small and large pupil sizes while maintaining the depth of field. Performances with L3 were equal to L2.

The use of a freeform surface can significantly reduce the impact of individual biometric variations such as corneal aberrations and transverse IOL positioning on EDOF behavior lenses, for small and large pupil sizes.