Effect of ciliary sulcus angle on the prediction of the vault for phakic implantable collamer lens in the KS formula.

Purpose: We aimed to explore the effects of the ciliary sulcus angle (CSA) on accurate prediction of the vault after phakic implantable collamer lens (EVO ICL Model V4c) using the KS formula.
Methods: Patients were classified according to the size of CSA: group A, narrow angle (CSA < 30°); group B, normal angle (CSA = 30-90°); and group C, wide angle (CSA > 90°). Further, differences between the actual vault dimensions at 3 months postoperatively and the preoperatively predicted vault dimensions in the three groups were analyzed.
Results: This study included 223 eyes of 223 individuals. In groups A-C, the difference in the preoperative vault dimensions of the three groups predicted with the KS formula was not statistically significant (P = 0.056). The actual vault dimensions at 3 months postoperatively were significantly different between the three groups (P < 0.001). Moreover, the difference between the actual and predicted vaults by the KS formula was statistically significant (P < 0.001). In the 3 months, after surgery, the percentages of patients with a low vault (< 250 μm) were 0%, 3%, and 29% in groups A, B, and C, respectively. Further, the percentages of patients with an ideal vault (250-750 μm) in the postoperative period were 66%, 84%, and 71% in groups A, B, and C, respectively. Finally, the percentages of patients with a high vault (> 750 μm) in the postoperative period were 34%, 13%, and 0% in groups A, B, and C, respectively. Notably, the distribution of the vault among the three groups was statistically significant (P < 0.001).
Conclusion: The size of CSA significantly affects the predictiveness of the vault by the KS formula, with the most pronounced effect on the angles < 30° and > 90°. Therefore, CSA should be considered when selecting the lens size using the KS formula preoperatively.
Clinical Trial Registration Number: ChiCTR2200065501.
(© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)