Refractive accuracy of the new Barrett formula using segmented axial length compared with that of the traditional Barrett Universal II formula.

Purpose: To compare the refractive accuracy of the Barrett True axial length (BTAL) formula, newly integrated into ARGOS, with that of the Barrett Universal II (BUII) formula calculated using axial length (AL) from IOL Master 700.

Setting: Private clinics in Kanagawa, Japan.

Design: Retrospective observational study.

Methods: We assessed eyes of patients who underwent cataract surgery with SY60WF IOL implantation, using ARGOS and IOL Master 700. The predicted refraction for BTAL was back-calculated. Refractive prediction errors (RPEs) for BTAL, BUII with ARGOS (segmented BUII), and BUII with IOL Master 700 (composite BUII) were compared. We primarily aimed to demonstrate the non-inferiority of BTAL to composite BUII in absolute RPE.

Results: We included 209 eyes from 209 patients. BTAL met the non-inferiority criteria, as the upper confidence interval (CI) boundary was below the non-inferiority margin of 0.10 diopters (D) for the difference in absolute RPE (-0.03 D; 95% CI: -0.06 to 0.01). In short eyes (AL ≤ 22.5 mm), the median absolute RPEs for BTAL, segmented BUII, and composite BUII were 0.25, 0.18, and 0.37 D, respectively, with significant differences between BTAL and composite BUII (p = 0.028) and segmented BUII and composite BUII (p = 0.018). In long eyes (AL > 26 mm), the median absolute RPEs were 0.21, 0.20, and 0.28 D for BTAL, segmented BUII, and composite BUII, respectively.

Conclusions: BTAL was non-inferior to composite BUII in absolute RPE. BTAL is an accurate and useful intraocular lens power calculation formula, even in eyes with short and long AL.