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

Objective: 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, R2 = 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.].