Repeatability and agreement of 4 biometers measuring corneal astigmatism in eyes with irregular corneal astigmatism component

Purpose To investigate the repeatability and agreement of corneal astigmatism measurements in eyes with irregular corneal astigmatism component (ICAC) using four devices: IOLMaster 700 biometer, Lenstar 900 biometer, iTrace, and Pentacam. Design Prospective cross-sectional reliability analysis. Methods Sixty-four eyes (52 patients) with ICAC were examined three times using the four devices. The eye with ICAC in this study is defined as the cornea has a certain degree of irregular astigmatism (asymmetric and/or skewed bowtie pattern of corneal topography according to corneal topography classification), accompanied with total corneal higher-order aberrations in the 4 mm zone of 0.3 μm or greater. Corneal astigmatism was evaluated using three categories: anterior corneal astigmatism (ACA), posterior corneal astigmatism (PCA), and total corneal astigmatism (TCA). The repeatability was determined using the ∆Ast (arithmetic mean of vector differences among three repeated corneal astigmatism measurements). Bland-Altman plots and astigmatism vector analyses were employed to assess agreement. Results The IOLMaster 700 (∆Ast=0.27±0.20D) showcased higher repeatability in ACA measurements compared to iTrace (∆Ast=0.37±0.38D, P=0.040) and Pentacam (∆Ast=0.50±0.22D, P<0.001), and paralleled the performance of Lenstar 900 (∆Ast=0.31±0.26D, P=0.338). The Pentacam (∆Ast=0.09±0.07D, P<0.001) demonstrated superior repeatability in PCA, whereas the IOLMaster 700 (∆Ast=0.33±0.23D, P<0.001) excelled in TCA. The IOLMaster 700 exhibited good agreement with either Lenstar 900 or iTrace, characterized by narrow 95% limits of agreement and clinically acceptable vector differences. Conversely, vector differences between Pentacam and the other three devices in ACA and TCA measurements were clinically significant, exceeding 0.50D(all P<0.05). Conclusions In terms of repeatability of corneal astigmatism measurements in eyes with irregular corneal astigmatism component, the IOLMaster 700 and Lenstar 900 outperformed iTrace and Pentacam. While the IOLMaster 700 can be used interchangeably with either Lenstar 900 or iTrace, the Pentacam is not interchangeable with the other three devices.