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Ray-Tracing-Based Intraocular Lens Power Calculation in Combined Cataract Surgery and Descemet Membrane Endothelial
Jan O Weber1, Klemens P Kaiser1, Jascha A Wendelstein2,3,4
1Department of Ophthalmology, Goethe-University, Frankfurt, Germany.
Background:
To compare the predictive accuracy of ray tracing-based intraocular lens (IOL) power calculation formulas with the Barrett Universal II (BUII) formula in eyes with Fuchs endothelial corneal dystrophy (FECD) undergoing combined cataract surgery and Descemet membrane endothelial keratoplasty (triple DMEK).
Methods:
This is a retrospective, single-centre comparative case series. Preoperative biometry was obtained using Scheimpflug tomography (Pentacam AXL) and a swept-source optical coherence tomography-based biometer (IOLMaster 700). IOL power calculations were performed using Barrett Universal II (BUII), Olsen ray-tracing and two OKULIX ray-tracing approaches (paraxial and 2.5-mm pupil). Prediction error (PE) was calculated and trueness, precision, and accuracy were evaluated using robust statistical methods (Eyetemis). A retrospective IOLup1D adjustment was additionally assessed.
Results:
One hundred forty-nine eyes of 149 patients were enrolled. BUII demonstrated the lowest trimmed mean absolute error (0.74 ± 0.65D) and median absolute error (0.60D), with 72% of eyes within ±1.00D of the target refraction. Olsen ray-tracing showed higher errors (mean absolute error 1.06 ± 1.02D), while both OKULIX approaches performed similarly (0.91-0.92D). Only OKULIX paraxial ray-tracing showed no significant systematic bias (p = 0.450), whereas all other formulas demonstrated a significant hyperopic shift (p < 0.001). After retrospective IOLup1D adjustment, BUII and Olsen achieved comparable accuracy, with Olsen demonstrating the highest trueness. Mean keratometry values measured with the IOLMaster were 0.20 ± 0.63D steeper compared to the Pentacam.
Conclusion:
In triple DMEK eyes, ray tracing-based IOL power calculation did not offer better accuracy compared to BUII. BUII demonstrated the highest accuracy and precision overall. After IOLup1D adjustment, BUII and Olsen achieved comparable accuracy, with Olsen showing the greatest trueness.
