Spherical equivalent prediction analysis in intraocular lens power calculations using Barrett Universal II formula variations

PURPOSE: To evaluate the prediction accuracy of the Barrett Universal II (BUII) intraocular lens (IOL) formula variations, including optional biometric parameters and sum-of-segments (SOS) axial length (AL) modification, for IOL power calculation in cataract surgery. SETTING: Single-center academic university hospital. DESIGN: Retrospective case series. METHODS: 1340 eyes of 1340 patients undergoing uneventful cataract surgery were analyzed using 5 BUII variants: with only 1 optional parameter (lens thickness [BUII LT] or white-to-white [BUII WTW]), 2 optional parameters (BUII STD), without optional parameters (BUII WØ), and adjusted for SOS AL (BUII TAL). A single swept-source optical biometer (ARGOS) was used. Spherical equivalent prediction error (SEQ-PE, trueness), SD (precision), and absolute SEQ-PE (accuracy) were calculated with the online Eyetemis tool. Statistical comparisons were conducted using robust statistical methods across the entire cohort and subgroups based on AL: short (<22.0 mm), average (22.0 to 24.99 mm), and long (≥25.0 mm). RESULTS: All formula variations showed high refractive accuracy. BUII TAL provided superior precision and best accuracy, particularly outperforming other variants in short eyes ( P < .01). For average and long eyes, accuracy and precision differences between the modified BUII TAL and standard BUII STD were minimal and not statistically significant. The percentage of eyes within ±0.50 diopters prediction error was highest for BUII TAL and BUII STD (80%), slightly outperforming other variants. CONCLUSIONS: BUII formula variants demonstrated excellent refractive prediction accuracy. SOS adjustment and optional biometric parameters notably improved precision and accuracy, especially in short eyes.