Accuracy of Intraocular Lens Calculation Formulas for the Four-Flanged Fixation Technique in Eyes With No Capsular Support

PURPOSE: To assess the refractive prediction error of four intraocular lens (IOL) calculation formulas in eyes that have undergone scleral fixation using the four-flanged technique. METHODS: This was a retrospective cohort analysis of patients who underwent scleral fixation using the four-flanged technique at the Shamir Medical Center between 2020 and 2021. Refractive prediction errors for four IOL prediction formulas (Barrett Universal II, Holladay 1, SRK/T, and Kane) were obtained by subtracting the predicted spherical equivalent from the postoperative spherical equivalent. Mean arithmetic refractive prediction error and mean absolute error were calculated and compared. RESULTS: Twenty-three eyes of 23 patients were included in the analysis. The Akreos AO60 IOL (Bausch & Lomb, Inc) was implanted in 9 eyes and the BunnyLens HP IOL (Hanita Lenses) in 14 eyes. Mean age was 72.84 ± 13.2 years. All formulas produced myopic mean arithmetic refractive prediction error. Mean arithmetic refractive error and mean absolute error were equal in absolute number. Mean arithmetic refractive prediction errors were -0.72 diopters (D) for Barrett Universal II, -0.61 D for Holladay 1, -0.77 D for SRK/T, and -0.94 D for Kane formulas. The refractive outcome differed significantly from the predicted refraction in all formulas. There were no statistically significant differences in prediction errors between the formulas. CONCLUSIONS: Refractive outcomes of the four-flanged fixation technique produced myopic results compared to the predicted refraction for all formulas tested. This suggests that the effective lens position is more anterior than in-the-bag IOL implantation.