Analysis of Inter-Eye Vault Differences After Implantable Collamer Lens (V4c) Implantation

PURPOSE: The safety and stability of implantable collamer lens (ICL) implantation are closely related to the vault. We aimed to assess clinical data from patients with similar anterior segment anatomy who received ICL of the same model placed in the same position and analyze common range and factors affecting the vault inter-eye difference. PATIENTS AND METHODS: A prospective study was performed, including 162 eyes of 81 patients with a bilateral ICL (V4c) implantation. Subjects were evaluated before the surgery and 1 day, 1 week, and 1 month postoperatively, and they were divided into 4 groups based on the ICL size. Bivariate correlation and multiple linear regression (stepwise) analyzed associations between vault inter-eye differences and horizontal sulcus-to-sulcus diameter, anterior chamber depth, lens thickness, ICL size, spherical equivalent, and vault. RESULTS: One month after surgery, mean vault inter-eye differences were 74.59 ± 55.59 µm. Nearly 70% of patients presented with vault inter-eye differences lower than 100 µm. The second eye vault variance of 69% was attributed to the first eye vault. Vault inter-eye differences were positively correlated with ICL spherical equivalent (regression equation: vault inter-eye differences (μm) = 139.415 + 6.295 × ICL spherical equivalent). Vaults after ICL implantation were similar in fellow eyes, with some considerable differences. The 95% confidence interval of the vault inter-eye difference was −34.4 ~ 183.6 μm. CONCLUSION: In eyes with similar anterior segment anatomy, there is a 95% probability that the vault will vary from −34.4 μm to −183.6 μm when a similar ICL is implanted. These results can help surgeons to select an appropriate ICL size to achieve an ideal vault. The smaller the spherical equivalent, the larger the difference between the two vaults, which provides a reference for size in moderate myopia. ICL spherical equivalent affects and predicts vault inter-eye differences after ICL implantation.