Quantitative analysis of iris–ciliary angle area to optimize ICL selection: a retrospective study

To introduce the iris-ciliary angle area (ICAA) as a novel quantitative parameter for enhancing accuracy in implantable Collamer lens (ICL) sizing and postoperative vault prediction, addressing limitations of traditional methods based on white-to-white (WTW) and anterior chamber depth (ACD), particularly in high myopia cases. In this retrospective study of 319 eyes, sulcus-to-sulcus (STS), ICAA, and other ocular parameters were analyzed using multivariate linear regression models to assess their influence on ICL diameter and vault. Clinical validation was conducted to compare the predictive accuracy of the proposed model with conventional sizing methods. STS was identified as an independent predictor of ICL size, while ICAA, STS, axial length (AL), and ICL size were significant predictors of postoperative vault. The proposed model demonstrated significantly reduced vault prediction errors (75.06 ± 66.43 μm) compared to the NK formula (210 ± 155 μm), NK2 formula (201 ± 146 μm), and Staar nomogram (189 ± 132 μm) (P < 0.001), despite moderate R² values, indicating improved clinical precision in ICL optimization. ICAA and STS offer valuable additions to ICL selection criteria, significantly improving vault prediction accuracy compared to established formulas, with approximately 60–64% reduction in mean absolute error. The quantitative assessment of posterior chamber structures through these parameters enhances procedural reliability and surgical outcomes. Further validation is recommended for cases involving extreme vaults or rotated ICL implants to confirm the model's broad applicability.