Horizontal And Vertical Ciliary Sulcus Diameter Difference (Cs Diff)---A New Indicator For Icl Size Selection And Vault Prediction

Implantable Collamer Lens (ICL) surgery corrects refractive errors by implanting a posterior chamber phakic intraocular lens. Traditional measurement methods rely on parameters such as anterior chamber depth (ACD) and corneal diameter (white-to-white, WTW), but individual anatomical variations often lead to prediction deviations. This study aims to explore the morphological characteristics of the posterior chamber space in the coronal plane and its impact on postoperative vault after ICL implantation. We propose the horizontal and vertical ciliary sulcus diameter difference (CSDiff) as a new evaluation metric to optimize ICL size selection and predict postoperative vault.

Recent anatomical studies have revealed significant spatial heterogeneity in the morphology of the ciliary sulcus,with differences in horizontal and vertical diameters potentially directly affecting the centration, tilt, and vault distribution of the ICL.This study proposes CSDiff as a new metric for ICL size selection and vault prediction, aiming to optimize the three-dimensional fit of the ICL by quantifying the anatomical differences between the horizontal and vertical ciliary sulcus.

The study collected data from 756 patients who underwent ICL implantation between October 2024 and January 2025. Preoperative measurements of horizontal ciliary sulcus diameter (STS-H) and vertical ciliary sulcus diameter (STS-V) were taken using UBM.The coronal plane was mapped, and the difference between STS-H and STS-V (CSDiff, denoted as ΔHsts-Vsts) was calculated. Other parameters included lens anterior convexity (STSL), and postoperative vault measured by OCT . Using a random forest algorithm, CSDiff and 14 other ocular parameters were input into a machine learning model to screen for key predictive factors and validate the sensitivity and specificity. The predictive ability of CSDiff for postoperative vault was further validated.

ΔHsts-Vsts value showed a positive correlation with postoperative vault (r=0.369), and its predictive performance was significantly better than ACD (r=0.043) and WTW (r=0.027). There were statistically significant differences among different ICL size (12.1size 0.488±0.189;12.6size 0.608±0.201;13.2size 0.690±0.232;13.7size 0.789±0.256) (p<0.05). The machine learning model incorporating ΔHsts-Vsts achieved a prediction accuracy of 82.5% for postoperative vault (36.122±21.236μm). In the high vault group (>1000μm), the value was 0.242±0.101, significantly lower than that in the ideal vault group (0.642±0.123). Applying ΔHsts-Vsts for ICL size selection, the rate of ICL replacement due to vault abnormalities decreased from 2.2% to 0.8% (P<0.05).

The posterior chamber space of the human eye exhibits a vertically oval shape in the coronal plane. CSDiff can serve as an important reference metric for ICL size selection and postoperative vault prediction. By preoperatively assessing CSDiff, surgeons can more accurately predict postoperative vault and optimize ICL size selection, thereby reducing the risk of postoperative complications. However, it should be noted that excessive lens anterior convexity (STSL > 0.5) is associated with a higher risk of low vault. This study provides a new theoretical basis for the precision and personalization of ICL surgery.