Comparison of 11 Intraocular Lens Power Calculation Formulas in Eyes Undergoing Simultaneous Cataract Surgery and Descemet Membrane Endothelial Keratoplasty

PURPOSE: To evaluate the accuracy of 11 intraocular lens (IOL) calculation formulas in eyes undergoing Descemet membrane endothelial keratoplasty (DMEK) combined with cataract surgery (triple DMEK). DESIGN: Retrospective accuracy and validity analysis with a consecutive case series. METHODS: We included Eighty eyes of 80 patients (52 females, 28 males) with a mean age of 67.08 ± 7.64 years (range: 45-83 years) receiving triple DMEK at the Department of Ophthalmology, Goethe University, Frankfurt, Germany, between 2016 and 2023. Preoperative biometry measurements were obtained from IOLMaster 700 (Carl Zeiss Meditec). Statistical evaluation was performed by comparison of the mean prediction error (ME) and the mean and median absolute prediction error (MAE and MedAE). Calculations were performed with and without adjustment by the IOLup1D method for all formulas. RESULTS: Adjusted IOLup1D formulas showed better results than the unadjusted formulas. The MedAE was lowest for Barrett Universal II (IOLup1D) (0.64 diopters [D]) followed by Postoperative spherical Equivalent prediction using ARtificial intelligence and Linear algorithms, by Debellemaniére, Gatinel, and Saad (IOLup1D) (0.66 D), Emmetropia Verifying Optical (IOLup1D) (0.67 D), Holladay 2 (IOLup1D) (0.70 D), Hoffer Q Savini/Taroni (IOLup1D) (0.71 D), Kane (IOLup1D) and T2 (IOLup1D) (0.72 D each), and Haigis (IOLup1D) and Holladay 1 (IOLup1D) (0.73 D each). The highest MedAE were found with Hill-Radial Basis Function (IOLup1D) and Sanders-Retzlaff-Kraff/theoretical (IOLup1D) (both 0.74 D). Regarding eyes within prediction errors of ±0.50 D, again Barrett Universal II (IOLup1D) (40.0%) performed best. The lowest percentage of eyes within a predicted refraction of ±0.50 D were seen with the Emmetropia Verifying Optical (IOLup1D), Kane (IOLup1D), and Holladay 2 (IOLup1D) (33.8% each). CONCLUSION: Prediction of the postoperative refraction in eyes requiring cataract surgery and DMEK is still challenging and not as accurate, as in healthy eyes without corneal abnormalities. In our case series, the Barrett Universal II formula achieved the overall best results. Although not statistically significant, this outcome should be taken into account when calculating IOL power in patients undergoing cataract surgery combined with DMEK.