Refractive Prediction Error After Intrascleral Intraocular Lens Fixation in Eyes with Long Axial Length

Purpose: To evaluate the refractive prediction accuracy of intraocular lens (IOL) power calculation formulas after flanged intrascleral IOL fixation(SF-IOL; Yamane technique) in long axial length (AL) eyes. Setting: The University of Osaka Hospital, Osaka, Japan. Design: Retrospective observational cohort study Methods: Eyes undergoing SF-IOL between January 2023 and April 2024 were classified into normal (N, <26.0 mm) and long (L, ≥26.0 mm) AL groups. Barrett Universal II, Hoffer Q, Holladay 1, and SRK/T were evaluated. Prediction error (PE) was defined as 3-month postoperative spherical equivalent minus predicted value. Prediction accuracy was assessed using root mean square absolute error (RMSAE) and the Formula Performance Index (FPI). Results: Fifty-three eyes from 50 patients were analyzed (N=35; L=18). Mean AL was 24.6±0.8 mm (N) and 27.1±1.0 mm (L). Mean PE (N and L) was −0.55±0.72 D and −0.64±0.62 D with Barrett Universal II (P=0.52), −0.68±0.77 D and −0.45±0.62 D with Hoffer Q (P=0.32), −0.78±0.74 D and −0.31±0.72 D with Holladay 1 (P=0.043), and −0.74±0.72 D and −0.62±0.72 D with SRK/T (P=0.60). In L group, Holladay 1 showed PE nearest zero; however, demonstrated steep AL–PE regression slope and low FPI. Barrett Universal II yielded the lowest RMSAE and the highest FPI. Conclusion: Barrett Universal II demonstrated the highest overall predictive accuracy in long AL eyes undergoing SF-IOL. Although Holladay 1 produced a smaller PE in long AL, this reflected systematic offset rather than superior accuracy, as indicated by its lower FPI.