Objective To assess the reliability of ocular component measurements with a new optical biometry device (AL-Scan; Nidek) and compare these measurements with those of the IOLMaster (Carl Zeiss Meditec) in patients with cataract.

Methods Sixty-eight cataractous eyes of 68 patients were included in the prospective study. To assess AL-Scan repeatability and reproducibility, central corneal thickness, anterior chamber depth (ACD), keratometry (K) over 2.4 mm and 3.3 mm diameter, axial length (AL), white to white (WTW), and pupil distance (PD) values were measured by two operators. ACD, K, AL and WTW were also measured with the IOLMaster to investigate the level of agreement. Calculations of intraocular lens (IOL) power were compared between the two devices.

Results AL-Scan measurements were highly repeatable and reproducible, except for WTW and PD. Bland–Altman analysis showed good agreement between devices for AL, ACD and most K values. Compared with the IOLMaster, AL-Scan-derived K values using a diameter of 2.4 mm showed a narrower 95% limit of agreement (LoA) than those obtained with a diameter of 3.3 mm. However, poor agreement of WTW measurements was found. The 95% LoAs between devices for IOL calculations were smaller when based on AL-Scan K measurements using a diameter of 2.4 mm rather than 3.3 mm.

Conclusions The repeatability and reproducibility of AL-Scan was excellent for all parameters, except WTW and PD. Excluding WTW, good agreement was found between the AL-Scan and IOLMaster. The 2.4-mm diameter K value may be the most reliable choice for calculation of IOL power with the AL-Scan.