AIM: To determine the factors related to preoperative ocular characters that are predictive of insufficient vault (<250 μm) after implantable collamer lens (ICL V4c; STAAR Surgical) implantation. METHODS: The participants underwent ICL surgery and were divided into the low (<250 μm) and normal (250-1000 μm) vault groups based on the postoperative vault at 3mo. The preoperative biometric parameters and clinical outcomes were compared between the two groups. The relationship between the 3-month vault values and preoperative ocular parameters were evaluated by Generalized estimating equations. RESULTS: Sixteen (23 eyes) and 36 patients (63 eyes) were in the low and normal vault groups, respectively. All implantation procedures were uneventful with no cataract formation in the early postoperative period. The sulcus-to-sulcus lens rise (STSL) and iris ciliary angle (ICA) were correlated with vault at 3mo after surgery. Every 0.1 mm increase in STSL was associated with 38.9 μm decrease in the postoperative 3-month vault. A rise of 1 degree in ICA is associated with a reduction of 4 μm in vault. CONCLUSION: Eyes with a narrow ciliary sulcus are associated with a higher rate of low vault after ICL implantation, suggesting a need for adjustments to the ICL size in these patients. Evaluating the characteristics of the ciliary sulcus contributes valuable information to predict low vault after surgery.