Refractive Results Using a New Optical Biometry Device: Comparison With Ultrasound Biometry Data

The aim of the study was to compare the measurements of optical (AL-Scan; Nidek Co., Ltd.) and ultrasonic (Echo Scan US-800; Nidek Co., Ltd.) biometry devices and to assess refractive results after cataract surgery. Eighty-one cataractous eyes of 81 patients were included in this study. Biometry was performed using the AL-Scan and an ultrasonic biometer (USB). Axial length (AL), keratometry (K) data, and intraocular lens (IOL) power calculations using the SRK/T formula were compared. Bland–Altman analysis was used to assess the extent of agreement between AL-Scan and USB data in terms of AL measurement and IOL power calculation. The K measurements of the AL-Scan were compared to autorefractor data (Canon Autorefractor RK-F1). The AL-Scan assessed the AL as longer (average difference 0.06 ± 0.18 mm; ICC = 0.987; P < 0.001) and the IOL power as greater (average difference 0.19 ± 0.66 D; ICC = 0.964; P < 0.001) than the USB. The AL-Scan also measured average K values (average difference 0.25 ± 0.25 D; ICC = 0.985; P < 0.001) greater than those given by the autorefractor. The postoperative mean absolute error was +0.30 ± 0.04 D (minimum: −0.51 D, maximum +1.04 D). The postoperative mean K value change was 0.36 ± 0.29 D (P < 0.05). The differences between measurements afforded by the AL-Scan and USB may be clinically acceptable. Keratometric changes that develop after cataract operations compromise the attainment of good refractive outcomes.