# From ciliary sulcus asymmetry to vault prediction: an hSTS-based approach to individualized sizing of implantable collamer lenses in myopic eyes

## TL;DR

This study explores how the shape of the ciliary sulcus in myopic eyes affects implantable lens sizing and develops a model to predict post-surgery outcomes.

## Contribution

A novel predictive model for postoperative vault using hSTS and ICL size to improve individualized lens sizing in myopic patients.

## Key findings

- The ciliary sulcus is predominantly vertically elliptical in myopic eyes.
- Higher myopia is associated with larger hSTS and vSTS and a greater vSTS-hSTS difference.
- A prediction formula using hSTS and ICL size explains 65.7% of the variance in postoperative vault.

## Abstract

To investigate the distribution and correlations of horizontal and vertical sulcus-to-sulcus diameters (hSTS/vSTS) in myopic eyes with different refractive errors, and to develop a predictive model for postoperative vault after posterior chamber phakic implantable collamer lens (ICL) implantation based on key anterior segment parameters.

This retrospective study included two non-overlapping cohorts of myopic patients who underwent ICL implantation at a single tertiary eye hospital. The morphology cohort comprised 244 eyes, classified into moderate, high, and extreme myopia groups according to spherical equivalent (SE). Ultrasound biomicroscopy (UBM) was used to measure hSTS and vSTS; inter-group comparisons and correlation analyses were performed. The model development cohort included 44 patients (72 eyes). In addition to STS, preoperative anterior segment parameters (corneal curvature, horizontal corneal diameter, anterior chamber depth, lens thickness, and axial length) were recorded, and ICL size was selected according to the STAAR nomogram. One month postoperatively, the vault was measured using anterior segment optical coherence tomography. Univariate correlation and stepwise multiple linear regression were applied to identify factors and derive a prediction formula.

The ciliary sulcus was predominantly vertically elliptical in the overall population (vSTS > hSTS). In the extreme myopia group, both hSTS and vSTS were significantly larger than in moderate and high myopia groups, with a greater vSTS-hSTS difference (0.63 ± 0.38 mm, all P < 0.05). SE correlated weakly and negatively with hSTS (r = –0.177, P = 0.006) and vSTS (r = –0.243, P < 0.001), while hSTS and vSTS were strongly positively correlated (r = 0.781, P < 0.001). In the modeling cohort, stepwise regression identified hSTS and ICL size as independent predictors of vault (adjusted R2 = 0.657), yielding the formula: vault (μm) = –2286.216 - 164.416 × hSTS (mm) + 375.487 × ICL size.

The higher myopic refractive error is associated with a more pronounced vertically elliptical ciliary sulcus. Routine measurement of both vertical and horizontal STS, combined with a vault prediction model based on hSTS and ICL size, may facilitate individualized ICL sizing, improve vault predictability, and enhance surgical safety.