Effect of Intraocular Lens Power Calculation Formula Optimization in the Sum-of-Segments Optical Biometer.

Purpose: We evaluated the effect of optimization of the intraocular lens (IOL) power calculation formula SRK/T and Barrett Universal II (BU II) in long eyes (≥26 mm: group L) and short eyes (≤22 mm: group S) using axial length calculated from segmented refractive indices (SRI).

Setting: Multicenter study at five sites in Japan.

Design: Retrospective observational study.

Methods: This study included 461 eyes of 461 patients (mean age 73.8 ± 8.4 years) who underwent cataract surgery. The predicted refractive error (PRE) was compared between the SRI (ARGOS) and the equivalent refractive index (ERI) biometers (IOLMaster^TM700). The patients were randomly divided into two groups, a learning group and a validation group. The optimization constants were determined in the learning group, and the optimization constants were subsequently applied to the validation group and compared with the ERI biometer results.

Results: Using both SRK/T and BU II, the validation group's PRE using optimization constants for the SRI biometer in group L was significantly smaller than that using the ERI biometer (p<0.001, p<0.01). In group L, the arithmetic PRE of Barrett UII formula with SRI showed a significant improvement after optimization compared to before optimization (p<0.0001). In group S, the arithmetic PRE of SRK/T and Barrett UII formula with SRI showed a significant improvement (p<0.0001, p<0.0001).

Conclusion: In long and short eyes, the current study revealed that optimization of the SRK/T and Barrett formula constants for the SRI biometer was beneficial to achieve accurate refractive outcomes after cataract surgery.