Comparison of Anterior Segment Parameters and Axial Length Using Two Scheimpflug Devices with Integrated Optical Biometers

Abstract

Purpose: To assess the repeatability of anterior segment parameters and axial length (AL) using Pentacam AXL and Galilei G6 and the agreement between both devices.

Materials and methods: Eighty-four eyes of 84 participants were measured prospectively with two devices. Outcome measurements included corneal curvatures, anterior chamber depth (ACD), AL, pupil size, and white-to-white distance (WTW). Intra-device repeatability was assessed using intraclass correlation coefficient (ICC), within-subject standard deviation (Sw), test-re-test repeatability (TRT=2.77 Sw), and coefficient of variation (CoV). Agreement between two devices was analyzed using Bland-Altman plots.

Results: For each device, the Sw of corneal curvatures, ACD, and AL were lower than 0.25 D, 0.04 mm, and 0.04 mm, respectively. The ICC was higher than 0.90 in all parameters measured by Pentacam AXL, whereas three parameters measured by Galilei G6 (steep meridian at anterior and posterior cornea, and pupil size) were lower than 0.90. Comparing to Galilei G6, Pentacam AXL led to significantly lower mean anterior cornea curvatures (Km) with the mean difference (95% level of agreement; LoA) of -0.12 D (-0.36, 0.12, P<0.001). For ACD, there was no significant difference between the two devices. Pentacam AXL led to significantly lower AL, pupil size, and WTW, with the mean differences (95% LoA) of -0.04 mm (-0.35, 0.27), -0.18 mm (-0.71, 0.35), and -0.35 mm (-0.61, -0.10), respectively.

Conclusion: We found good repeatability of corneal curvature, ACD, and AL in both devices. Most parameters obtained from Pentacam AXL were statistically significantly different from those obtained from Galilei G6, except for steep meridians and ACD.

Keywords: Galilei G6; Pentacam AXL; agreement; intra-device repeatability.

Figure 1

Bland–Altman plots showing the agreements between anterior corneal parameters obtained by Pentacam AXL and Galilei G6: (A) K1 (flat K), (B) K2 (steep K), (C) Km (mean K), and (D) steep meridian. The solid line is the mean difference, the dashed lines are the 95% limit of agreement.

Figure 2

Bland–Altman plots showing the agreements between (A) axial length and (B) anterior chamber depth obtained by Pentacam AXL and Galilei G6. The solid line is the mean difference, The dashed lines are the 95% limit of agreement.