Evaluation of Barrett universal II formula for intraocular lens power calculation in Asian Indian population

ABSTRACT

Purpose: Barrett Universal II (BU-II) is considered as one of the most accurate intraocular lens (IOL) power calculation formulas; however, there is no literature studying the same in Indian population. The aim of this study was to evaluate the accuracy of BU-II formula in prediction of IOL power for cataract surgery in Asian Indian population. This was an institutional, prospective, observational study. Methods: Patients with senile cataract who underwent phacoemulsification with posterior chamber IOL implantation were enrolled in the study. Biometry data from Lenstar-LS900 was used and IOL power was calculated using four IOL formulas modified SRK-II, SRK/T, Olsen, and BU-II. Primary outcome was measured as the prediction error in postoperative refraction for each formula and secondary outcome was measured as the difference in mean absolute errors between the four formulas. SPSS Version-21 with P < 0.05 considered significant. Results: A total of 244 eyes were included in the study and were divided into three groups in accordance to axial length (AL) Group 1 (AL 22�.5 mm; N = 135), Group 2 (AL <22 mm; N = 53), and Group 3 (AL >24.5 mm; N = 56). BU-II formula gave the lowest mean absolute error (0.37 � 0.27D) and median absolute error (0.34) in predicted postoperative refraction in the entire study population. When compared with the other formulas, mean absolute error was significantly lower in all three groups (P < 0.0005) as well, except for Olsen formula in the normal AL group, where the results were comparable (P = 0.742). Conclusion: BU-II performed as the most accurate formula in the prediction of postoperative refraction over a wide range of ALs.