Comparison of a new implantable collamer lens formula to standards formulas using spectral domain optical coherence tomography.

Abstract

To use spectral-domain optical coherence tomography (SD-OCT) data to develop a new implantable collamer lens (ICL) sizing formula and compare vault outcomes with the Online Calculation and Ordering System™ (OCOS) and the NK2 formula. Consecutive eyes (n = 237) were evaluated that had undergone ICL/toric ICL implantation. Actual ICL vaults were measured, and a what-if analysis was performed to predict vault values with the NK2 formula using SD-OCT data. To develop a new formula (EPB), multiple regression analysis was performed with different parameters than the NK2 formula. Predicted vaults with NK2 and EPB formulas were compared to the actual vaults. Parameters that were correlated with optimal ICL size were white-to-white, anterior chamber width, lens rise and desired refractive correction. The mean postoperative vault was 489 ± 258μm. At last visit, 94.5% of eyes were within the manufacturer's acceptable vault range. Predicted vaults in the acceptable range were 74 and 87% with the NK2 and EPB formulas, respectively. Six percent had a predicted vault less than 100μm with the EPB formula compared to 1% for actual outcomes. The NK2 formula resulted in a shift toward higher predicted vaults while the EPB formula was similar to the actual postoperative vaults but with slightly more cases with extremely low and high vaults. SD-OCT data with OCOS result in good postoperative vaults. Further refinement is required to the NK2 for use with SD-OCT data. Although the EPB formula provides acceptable predicted vaults, further refinement with a larger sample size is needed.