Aberration-guided Intraocular Lens Power Calculation in Keratoconus: Ray Tracing Optimization

To evaluate the accuracy of ray tracing optimization (RTO) for predicting postoperative refractive error in keratoconic cataract eyes.

University Eye Clinic, Maastricht, the Netherlands.

Case series. Evaluation of technology.

Twenty-two keratoconic eyes who underwent cataract surgery were included in the study. Anterior and posterior corneal Zernike coefficients, axial distances, and intraocular lens (IOL) geometry were exported to custom-developed RTO algorithms to build patient-specific eye models. Optical quality was quantified with the Visual Strehl ratio (VSOTF). The defocus and astigmatism maximizing VSOTF were taken as the optimal target refraction and compared with postoperative subjective refraction using power vectors (SEQ, J0, J45). Agreement was assessed with Bland-Altman analysis, and prediction accuracy was summarized as the percentage within ±0.5D and ±1.0D.

Bland-Altman analysis showed good agreement between RTO-predicted and postoperative subjective refraction, particularly for SEQ (spherical equivalent) and J0 (with/against-the-rule astigmatism). The percentage of eyes within ±0.5D of prediction error was 68.2% for SEQ and J0 and 59.1% for J45; within ±1.0D it was 86.3% (SEQ), 81.8% (J0), and 77.3% (J45). Cataract surgery in keratoconic eyes did not induce significant variations in the corneal Zernike coefficients. RTO accuracy was highest when vertical coma (Z3-1) predominated as the main higher-order aberration.

Aberration-guided RTO provides accurate postoperative refractive predictions in keratoconic cataract eyes. Accuracy is particularly strong in eyes dominated by vertical coma, supporting inclusion of measured higher-order aberrations in IOL power selection.