Axial Length Dependency And Performance Of Iol Power Calculation Formulas In Yamane Intrascleral Haptic Fixation

To evaluate the predictive accuracy of various intraocular lens (IOL) power calculation formulas in eyes undergoing Yamane intrascleral haptic fixation and to investigate axial length (AL)–related refractive behavior. In particular, we aimed to determine whether Wang–Koch (WK) axial length adjustment reduces AL dependency and improves refractive outcomes in long eyes, as previously validated in standard in-the-bag cataract surgery.

Department of Ophthalmology, Yeouido St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea. Retrospective single-center study including consecutive cases undergoing Yamane intrascleral haptic fixation between December 2018 and July 2025.

This retrospective chart review included 205 eyes of 184 patients undergoing Yamane scleral fixation with a single IOL model (AR40e). Prediction error (PE) was defined as target refraction minus postoperative manifest refraction at 3 months. Mean error (ME), mean absolute error (MAE), median absolute error (MedAE), and percentages within ±0.25, ±0.50, ±1.00, and ±2.00 D were calculated. Formulas included Hoffer Q, Holladay 1, SRK/T (with and without WK adjustment), Barrett Universal II, EVO 2.0, and T2. Friedman test compared MAE among formulas. Linear regression assessed associations between PE and AL, horizontal corneal diameter (WTW), and mean keratometry.

Overall, statistically significant differences in MAE were observed among formulas (Friedman test, p=0.035), although absolute differences were small and no formula demonstrated consistent clinical superiority. Horizontal corneal diameter was not associated with PE in any formula. In contrast, AL showed significant associations with PE in several formulas, particularly in WK-adjusted models. In long eyes (AL ≥25 mm), WK adjustment did not improve MAE and was associated with increased myopic shift and stronger AL dependency. In eyes with AL <25 mm, differences among formulas were minimal.

In Yamane intrascleral haptic fixation, no single IOL formula showed clear clinical superiority. Axial length remained a significant determinant of refractive error, whereas horizontal corneal diameter had limited influence. Notably, Wang–Koch axial length adjustment did not eliminate AL dependency in long eyes and may induce overcorrection. These findings suggest that AL-related refractive behavior in Yamane fixation differs from standard in-the-bag cataract surgery, and caution is warranted when applying WK adjustment in scleral-fixated IOLs.