Koji-Sakamoto Versus Nakamura-Kunimoto For Vault Prediction In Icl Surgery: A Comparative Clinical Study

To evaluate and compare the reliability and clinical accuracy of the Nakamura-Kunimoto (NK) and Koji-Sakamoto (KS) formulas in predicting postoperative vault after Implantable Collamer Lens (ICL) surgery, and to assess their concordance with actual ICL size selection in clinical practice.

Vietnam Russia International Eye Hospital, Ho Chi Minh City, Vietnam.

This retrospective cross-sectional study included 52 eyes of 26 patients who underwent ICL V5 implantation between July and September 2025. Preoperative anterior segment parameters were measured using CASIA2 anterior segment optical coherence tomography (AS-OCT). Predicted vault values calculated using the NK and KS formulas were compared with actual vault measured at 1 month postoperatively. Concordance in ICL size selection among OCOS, NK, and KS was evaluated against the implanted lens size. Statistical analysis included paired t-test, mean absolute error (MAE), and Bland-Altman analysis.

The study included predominantly female patients (92.3%), mean age 22.7 ± 3.9 years, with mean myopia −11.59 ± 3.02 D. Mean anterior chamber depth was 3.56 ± 0.37 mm and white-to-white 11.65 ± 0.32 mm. Implanted ICL sizes were 12.1 mm (36.5%), 12.6 mm (55.8%), and 13.2 mm (7.7%).

Concordance with implanted size was 100% for OCOS, 71.2% for NK, and 46.2% for KS. In 32 eyes with 1-month vault data (646.6 ± 176.9 μm), NK underestimated vault (515.2 ± 176.0 μm, p = 0.004), whereas KS showed no significant difference (583.8 ± 134.0 μm, p = 0.070). MAE was lower with KS (144.3 μm) than NK (204.4 μm), indicating 29.4% higher accuracy. Ideal vault (250–750 μm) was more frequent with KS (87.5%) than NK (81.2%), particularly for the 12.6 mm size.

The Koji-Sakamoto formula demonstrated superior accuracy compared with the Nakamura-Kunimoto formula in predicting postoperative vault following ICL implantation, particularly for the 12.6 mm lens size. Integrating the KS formula alongside OCOS may enhance ICL size selection and optimize postoperative vault outcomes in clinical practice.