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.