Improving accuracy of phakic intraocular lens sizing using high-frequency ultrasound biomicroscopy.

PURPOSE To assess the efficacy of high-frequency ultrasound biomicroscopy (UBM) in improving the accuracy of phakic intraocular lens (pIOL) sizing by increasing the incidence of acceptable postoperative vault. SETTING Multiple private practices, United States. DESIGN Evaluation of diagnostic test or technology. METHODS This prospective multicenter clinical study evaluated eyes having pIOL (Visian Implantable Collamer Lens) implantation. A retrospective data analysis was performed using UBM measurements (VuMax-II) of preoperative sulcus-to-sulcus (STS) distance and postoperative vault. The regression data and clinical input from investigators were then used to develop a pIOL sizing nomogram. The nomogram used only STS and pIOL power as variables to determine length. Inadequate vault (<90 μm) and excessive vault (>1000 μm) were defined based on peer-reviewed literature. Sizing recommendations using the nomogram were studied prospectively and compared with 2 sizing methods used in the United States that are based on white-to-white (WTW) measurements. RESULTS One eye was excluded from the analysis because the wrong length pIOL was placed (12.6 mm instead of nomogram-recommended 13.2 mm), resulting in 51 μm of vault. The mean postoperative vault in the remaining 72 cases was 340 μm ± 174 (SD) (range 90 to 952 μm); there were no cases of inadequate or excessive vault with the newly developed UBM nomogram. Sizing methods using WTW measurements would have resulted in different-sized pIOLs in 36% to 69% of cases compared with the STS method. CONCLUSION There were no cases of inadequate or excessive vault when the UBM nomogram for pIOL sizing was used. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.