Refractive Error Prediction After Phacoemulsification Surgery: Lenstar LS 900 Versus Nidek AL-Scan

Purpose To compare the Lenstar LS 900 (Haag-Streit AG) and the Nidek AL-Scan (Nidek Co) optical biometry devices in intraocular lens (IOL) calculation and refractive error prediction in cases with uncomplicated phacoemulsification surgery. Methods In this study, axial length (AL), flat (K1), and steep (K2) axis, and the average (K-avg) keratometry values measured with the Lenstar LS 900 and the Nidek AL-Scan in patients who underwent uncomplicated phacoemulsification and the mean absolute error (MAE) of both devices were compared. Results One hundred five eyes of 105 patients were examined. AL was measured shorter with the Lenstar LS 900 than with the Nidek AL-Scan, and K1, K2, and K-avg were measured steeper ( P < .001 for all). Although there was no proportional bias in the AL, K1, and K-avg measurements of the Lenstar LS 900 and the Nidek AL-Scan devices ( P = .83, .96, and .41 respectively), there was a proportional bias in the K2 measurements ( P < .001, R 2 = 0.128). MAE was significantly higher in the Lenstar LS 900 (0.74 ± 0.6 D) than in the Nidek AL-Scan (0.64 ± 0.60 D) ( P < .001). The percentage of eyes with a prediction error within the range of ±0.50 D was significantly higher with the Nidek AL-Scan (61%) than with the Lenstar LS 900 (49.5%) ( P = .008). Conclusions The Nidek AL-Scan produced more predictable outcomes than the Lenstar LS 900 in selecting IOL power. Despite the clinical similarity between AL, K1, and K-avg readings, there may be notable differences in choosing the IOL power between these two devices. [ J Refract Surg . 2025;41(3):e257–e263.]