Retrospective Analysis of Factors Affecting Abnormal Vault after ICL Implantation

Objective: To analyze the factors that may lead to an abnormal vault after implantation of the implantable collamer lens (ICL). Methods: This research was based on the retrospective analysis of sixty patients (67 eyes) who underwent ICL V4c replacement after collamer lens implantation with a V4c lens in the Chengdu Aier Eye Hospital between November 2014 and November 2017. The replacement was performed because of abnormal vaults of the initial lens implantations, either less than 250 μm or more than 750 μm. Seventy patients (70 eyes) were randomly chosen as the control group from those who underwent ICL implantation during the same period and had normal vaults (250 to 750 μm). Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest refraction, intraocular pressure (IOP), corneal endothelial cell density (ECD), and lens thickness (LT) were measured before surgery. The posterior chamber angle, height of the ciliary processes (T value), sulcus-to-sulcus (STS) horizontal distance, STS vertical distance, and anterior chamber depth (ACD) were measured by an ultrasound biomicroscope (UBM). All patients were followed more than 6 months. UCVA, manifest refraction, BCVA, IOP, ECD, and vault height were measured. Data were analyzed using a t-test and multiple linear regression. Results: There were significant differences between the high vault group and the low vault group for posterior chamber angle and ICL size and ACD (all P<0.001). There were significant differences between the high vault group and normal vault group for ICL size and posterior chamber angle. Posterior chamber angle, ICL size, STS horizontal distance, T value, ACD, and LT were statistically significant factors for the abnormal vault (adjusted, R2=0.608, F=5.84, P<0.001). Eight eyes had a vault less than 250 μm after implantable collamer lens replacement in the low vault group. Whereas the vault was normal after ICL replacement in all eyes of the high vault group. There were no serious complications such as anterior subcapsular cataract, high intraocular pressure, or corneal endothelial decompensation during the observation period. Conclusions: Multiple ciliary sulcus factors affect vault after ICL implantation. T value, posterior chamber angle, STS horizontal distance, ACD, ICL size, and LT may be related to an abnormal vault. For cases where abnormal vault may occur, the ICL size can be determined in conjunction with the posterior angle to help achieve a proper vault. Key words: vault; posterior chamber angle; height of ciliary processes; lens thickness