Optimization of an Implantable Collamer Lens Sizing Method Using High-Frequency Ultrasound Biomicroscopy

Purpose To develop and evaluate a new implantable collamer lens (ICL) sizing method that uses high-frequency ultrasound biomicroscopy (UBM). Design Interventional case series. Methods ICL were implanted in 47 eyes of 25 patients (8 male, 17 female, mean age 34.7 ± 6.8 years). At 3 months after ICL surgery, the vault (distance between ICL and crystalline lens) was measured using anterior optical coherence tomography (OCT). Stepwise multiple regression analysis was performed in order to determine the optimal ICL size that will be expected to achieve a 0.5-mm vault, and the regression equation was calculated. Mean keratometric power, axial length, anterior chamber depth, sulcus-to-sulcus (STS) diameter, and distance between STS plane and crystalline lens were applied as candidates for explanatory variables. Subsequently, the equation was applied to a new group of patients (81 eyes of 43 patients, 20 male and 23 female, mean age 35.6 ± 7.2 years) in order to decide the ICL size. Postoperative vault was evaluated at 3 months after surgery. Main outcome measures were mean postoperative vault and percentages of eyes that achieved moderate vault. Results The regression equation was determined using 3 explanatory variables: anterior chamber depth (ACD), STS diameter, and distance between STS plane and anterior crystalline lens surface (STSL). The mean vault error (postoperative vault – predicted vault) was −0.06 ± 0.29 mm. Of the total number of eyes, 88.9% had a vault between 0.15 and 1.0 mm. None of the eyes had a low vault (1.0 mm). Conclusion A novel ICL sizing equation was developed and shown to be an effective method for calculation of the optimal ICL size in order to achieve an appropriate vault.