A UBM-Based Big Data Model for Individualized ICL Size Selection in Myopic Eyes

Abstract Background: Accurate prediction of post-operative vault is critical for safe and effective implantation of Implantable Collamer Lenses (ICLs). Traditional sizing methods rely on anterior segment parameters, such as white-to-white (WTW) and anterior chamber depth (ACD), are poorly correlated to the with sulcus-to-sulcus (STS) diameter where the ICL rests. Inappropriate sizing can result in suboptimal vaults, increasing the risk of complications. Ultrasound biomicroscopy (UBM) allows for direct assessment of posterior chamber structures but it has yet to be systematically integrated into predictive models at scale. Methods: We developed and validated a UBM-based, data-driven model for vault prediction using >2,000 ICL implantations performed between January 2023 and January 2025 at a single center. Pre-operative variables extracted from standardized UBM protocols include horizontal and vertical STS (STSH, STSV), lens curvature (LC), Posterior Chamber Angle (CSA) Morphology and Ciliary Process (CP) Size,. A random forest model was trained to identify dominant anatomical predictors. Based on these results, a posterior chamber asymmetry index (CS Diff = |STSH – STSV|) and empirically derived LC thresholds were used to construct a clinically practical ICL size selection chart. This chart was prospectively validated in 286 patients (568 eyes) operated between May and June 2025. Results: Random Forest and SHAP analyses identified STSH, STSV, LCH, and LCV as the most influential predictors. Higher CS Diff were associated with low vaults; greater LC predicted higher vaults. In the validation cohort, the selection map yielded ideal vaults (250–750 μm) in 92.96% of eyes. This represented a significant improvement over the historical WTW+ACD method (ideal rate <76.51>%, p<0.001). Decision-curve analysis demonstrated superior net clinical benefit across a wide range of threshold probabilities. Subgroup analyses confirmed robust performance, including in those with high-risk phenotypes (older age, shallow ACD, high LC). Conclusions: Posterior chamber geometry—especially STS asymmetry and lens curvature—drives vault variability more than traditional anterior segment metrics. Our validated UBM-guided model enhances individualized ICL sizing and significantly improves clinical outcomes. Adoption of such models into routine practice could reduce re-operations and establish a new standard of care in refractive surgery.