Comparison of the accuracy of 9 intraocular lens power calculation formulas after SMILE in Chinese myopic eyes

Abstract As of 2021, over 2.8 million cases of small incision lenticule extraction (SMILE) procedures had been performed in China. However, there remains limited knowledge regarding the selection of intraocular lens (IOL) power calculation formulas for post-SMILE cataract patients. This study included 52 eyes of 26 myopic patients from northern China who underwent SMILE at Tianjin Eye Hospital from September 2022 to February 2023 and was designed to investigate the performance of multiple IOL calculation formulas in post-SMILE patients using a theoretical surgical model. We compared the postoperative results obtained from three artificial intelligence (AI)-based formulas and six conventional formulas provided by the American Society of Cataract and Refractive Surgery (ASCRS). These formulas were applied to calculate IOL power using both total keratometry (TK) and keratometry (K) values, and the results were compared to the preoperative results obtained from the Barrett Universal II (BUII) formula in SMILE cases. Among the evaluated formulas, the results obtained from Emmetropia Verifying Optical 2.0 Formula with TK (EVO-TK) (0.40 ± 0.29 D, range 0 to 1.23 D), Barrett True K with K (BTK-K, 0.41 ± 0.26 D, range 0.01 to 1.19 D), and Masket with K (Masket-K, 0.44 ± 0.33 D, range 0.02 to 1.39 D) demonstrated the closest proximity to BUII. Notably, the highest proportion of prediction errors within 0.5 D was observed with BTK-K (71.15%), EVO-TK (69.23%), and Masket-K (67.31%), with BTK-K showing a significantly higher proportion compared to Masket-K (p < 0.001). Our research indicates that in post-SMILE patients, EVO-TK, BTK-K, and Masket-K may yield more accurate calculation results. At the current stage, AI-based formulas do not demonstrate significant advantages over conventional formulas. However, the application of historical data can enhance the performance of these formulas.