Comparison of three different instruments for vault measurements after implantable collamer lens implantation

To evaluate the differences and consistency of vault measurements obtained by Scheimpflug tomography (Pentacam), anterior segment optical coherence tomography (AS-OCT, CASIA II), and ultrasound biomicroscopy (UBM) following implantable collamer lens (ICL) V4c implantation.

Vault measurements were acquired using three modalities: Pentacam, CASIA II AS-OCT, and UBM. Repeated-measures analysis of variance was used to compare the vault values obtained by the three devices. The correlation and consistency of measurements among the three instruments were assessed using the Pearson correlation coefficient, intraclass correlation coefficient (ICC), and Bland-Altman plots.

This retrospective study enrolled 210 myopic eyes of 210 patients (158 women and 52 men) who underwent ICL implantation: 108 eyes had a myopic ICL V4c implanted, and 102 eyes had a toric ICL V4c implanted. The mean vault values measured by Pentacam, CASIA II, and UBM were 452.64±204.20 µm, 538.57±203.54 µm, and 560.95±227.54 µm, respectively, with statistically significant differences among the three groups (P<0.05). Pearson correlation analysis showed strong positive correlations between vault values measured by different instruments (all P<0.001). ICC results indicated good consistency among the three measurement modalities (all P<0.001). Stratified analysis revealed that when the vault value was ≤250 µm, the correlation and consistency of measurements across the three instruments were lower than those in the medium and high vault subgroups.

Vault values measured by Pentacam are lower than those obtained by CASIA II and UBM, with UBM yielding the highest mean vault values. Measurements from the three instruments are not interchangeable but can serve as mutual references due to their significant correlation and good overall consistency. Pentacam and CASIA II demonstrate the highest consistency in vault measurement. Notably, when the vault value is ≤250 µm, the consistency between Pentacam and the other two instruments decreases significantly.