AIM: To explore the accuracy and consistency of predicting postoperative vault in implantable collamer lens(ICL)surgery based on the NK and KS formulas of CASIA2 OCT.METHODS: Retrospective case study. The study included 85 patients(170 eyes)who underwent ICL implantation for the correction of moderate to high myopia at the Refractive Surgery Center of Lunan Eye Hospital from October 2022 to October 2023. Routine examinations including ultrasound biomicroscopy(UBM), corneal endothelium assessment, optometry, intraocular pressure measurement, fundus examination, and corneal topography were performed. Patients who met the indications for ICL surgery were selected, and the recommended lens size was determined based on parameters such as corneal diameter and anterior chamber depth using standard methods. A CASIA2 OCT examination was used to obtain the corresponding lens size and predicted vault using the NK and KS formulas. The differences and consistency between the predicted vault by NK and KS formulas and the actual vault at 1 wk, 1, 3, and 6 mo postoperatively were analyzed. Paired t-tests were used to analyze the differences between the predicted vault by NK and KS formulas and the actual vault at each postoperative time point. The consistency between the predicted vault by NK and KS formulas and the actual vault at each time point was assessed using Bland-Altman analysis. Multivariate linear regression was used to analyze the correlation between actual vault and various anterior segment parameters.RESULTS: The NK formula showed statistically significant differences between the predicted values and the actual vault at 1, 3, and 6 mo postoperatively(all P<0.05), but no statistically significant difference was observed compared to the actual vault at 1 wk postoperatively(P=0.340). The KS formula demonstrated a statistically significant difference between the predicted values and the actual vault measured at 6 mo postoperatively(P<0.05). The lens vector height and lens model were influcing facotrs for the vault at 6 mo postoperatively(all P<0.05). Both the NK formula and KS formula had the highest consistency between their predicted vault and the actual vault at 6 mo postoperatively.CONCLUSION: The NK and KS formulas of CASIA2 OCT showed the highest consistency between the predicted postoperative vault and the actual vault at 6 mo postoperatively. Both formulas can serve as effective references for ICL model selection.