Comparison of two swept-source optical biometers in eyes with long axial length

To assess the repeatability and agreement of two swept-source optical coherence tomography (SS-OCT)-based biometers when measuring biometric parameters in cataract eyes with a long axial length.

Cross-sectional prospective, comparative study.

One-hundred and twenty-six eyes of 126 patients with cataracts (LOCS III grade equal or less than 3) and axial lengths >25 mm were measured 3 consecutive times using the Argos and IOLMaster 700 SS-OCT optical biometers. Keratometry [K1 (flat) and K2 (steep)], central corneal thickness (CCT), white-to-white (WTW), anterior-chamber-depth (ACD), lens-thickness (LT), and axial length were measured using both instruments. The repeatability for each device was analysed with the within-subject standard deviation (Sw), coefficient of variability, and coefficient of repeatability, and the agreement between the devices was analysed using a Bland-Altman plot.

The acquisition success rate for both biometers was 100%. For K1 and K2, the Sw values were <0.15D and <0.2D, respectively using the two instruments. For CCT, WTW, ACD and LT, the values were 6.56 μm, 0.05 mm, 0.01 mm and 0.01 mm with the Argos, and 3.54 μm, 0.07 mm, 0.01 mm and 0.01 mm with the IOLMaster 700. The Sw values for axial length were 0.01 and 0.03 mm for the Argos and IOLMaster 700, respectively. There were statistically significant differences between the two SS-OCT biometers for all the parameters evaluated (p < 0.001) except WTW (p = 0.088). The mean differences for K1, K2, CCT, WTW, ACD, LT and axial length were 0.102D, 0.133D, -14.224 μm, -0.018 mm, 0.108 mm, 0.029 mm, and -0.102 mm, respectively.

Both SS-OCT biometers provide repeatable measurements for the different parameters analysed, however, when compared, it is clear that some of them must be assessed carefully in order to be considered interchangeable.