Vault of the phakic intraocular lens during vertical and horizontal fixation within patient comparison

This study aimed to compare the postoperative vault and preoperative predictions between vertical and horizontal fixation of implantable collamer lenses (ICLs). In this prospective case series, 63 patients (126 eyes) who underwent bilateral ICL insertion for myopia were randomly assigned to either horizontal or vertical fixation for each eye. An additional control group consisted of 63 patients receiving bilateral horizontal non-toric ICL fixation. Biometric measurements, including anterior chamber depth (ACD) and vault, were obtained using anterior-segment three-dimensional optical coherence tomography preoperatively and at 2 h, 1 day, 1 week, and 1 month postoperatively. ACD values remained stable and similar between both groups (P > 0.05). However, vault values were consistently lower in the vertical group than in the horizontal group at all time points (P < 0.001). The vault difference between preoperative predictions and actual measurements was significantly larger in the vertical group compared to the horizontal group (P < 0.001). The intergroup vault difference was significantly larger than the left-right eye difference in the control group (P < 0.001). Vertical ICL fixation reduced the vault by approximately 150 microm compared to horizontal fixation, a deviation from preoperative predictions, which should be considered when determining ICL size.