The Ciliary Process-Posterior Angle Complex: A Novel Risk Factor For Hyper-Vault After Icl Implantation – A Ubm-Based Analysis Of 2,000+ Eyes

 To develop a digital predictive model reflecting posterior chamber geometry (e.g., sulcus-to-sulcus [STS] asymmetry, lens curvature) by integrating direct UBM measurements of the ciliary sulcus. We aim to investigate how ciliary process size (CP) and posterior chamber angle morphology (CSA), beyond STS diameter, contribute to abnormal postoperative vault and to identify independent risk factors for extreme vaults.

Postoperative vault is critical for ICL safety, yet WTW/ACD-based sizing often yields poor predictability. High-resolution UBM visualizes posterior chamber morphology, but these data remain clinically underutilized without systematic predictive models. Quantitative evidence linking ciliary process morphology and posterior chamber angle to haptic positioning is lacking. Integrating UBM data into robust machine learning models is essential for personalized ICL sizing.

A UBM-driven vault prediction model was developed and validated using data from 2,000+ ICL surgeries (Jan 2023-Jan 2025). Preoperative parameters extracted included horizontal/vertical STS (STS-H, STS-V), lens curvature (LC), ciliary sulcus angle (CSA), and ciliary process size (CP). A random forest model identified dominant anatomical predictors, leading to the creation of a clinical ICL sizing atlas incorporating a sulcus asymmetry index (CS Diff = |STS-H – STSV|) and empirical LC thresholds. The atlas was prospectively validated in 286 patients (568 eyes) from May-June 2025. Retrospective case analysis was performed on eyes with postoperative extreme vaults.

Random forest and SHAP analysis identified STS-H, CP, CBTmax, STS-V, LC-H, and LC-V as key numerical predictors. The importance scores for posterior chamber morphology (CP, CBTmax) ranked second only to STS-H. In the validation cohort, 92.96% of eyes achieved an ideal vault (250–750 µm) using the atlas, significantly outperforming traditional WTW+ACD methods. Among 9 patients with postoperative hyper-vault, 8 had preoperative UBM reports indicating larger CP (0.827±0.213mm vs. 0.546±0.337mm in controls, p<0.001) and narrower CSA (22.859±4.562° vs. 39.983±8.736°, p<0.001). Two patients required ICL exchange due to narrow nasal anterior chamber angles; both had preoperative UBM showing narrow nasal posterior angles and large ciliary bodies.

Postoperative ICL vault is determined not only by STS diameter but also by the 3D configuration of the ciliary process-posterior angle complex. A "large ciliary process combined with a narrow posterior angle" is a key anatomical risk factor for hyper-vault, likely because the ciliary processes occupy posterior chamber space, forcing the ICL optic anteriorly. The UBM-driven atlas and identification of this high-risk complex enable preoperative recognition of vulnerable anatomy, facilitating optimized ICL size selection.