Intra- and Inter-Observer Agreement of a Portable A-Scan Ultrasound Biometer in Sitting and Supine Positions and Validity Against an Optical Biometer.

Purpose: The purposes of this study were to test the validity of a portable ultrasound biometer (6000 Scanmate-A, DGH Technology) against an optical biometer and to establish its repeatability and reproducibility on patients in sitting and supine positions.

Patients and methods: Healthy adults (N = 51) were recruited prospectively. At two study visits, Observer 1 made five measurements of AL and ACD in the right eye using an optical biometer (IOLMaster, Zeiss). Then two sets of three measurements of AL and ACD were made using the Scanmate-A, one while participants were sitting and another while they were supine. Observer 2 made the same measurements at one visit on a subset of participants (n = 42). Averages of the measurements were prepared for analysis (significance threshold set to α = 0.01) according to Bland and Altman, repeated-measures analyses of variance, linear correlations, and intraclass correlation coefficients (ICC).

Results: AL and ACD were significantly shorter when measured by the Scanmate-A (median [interquartile range] = 23.4 [22.5, 24.7] mm and mean ± standard deviation = 3.22 ± 0.45 mm, respectively) than when measured by IOLMaster (23.8 [23.1, 25.2] mm and 3.51 ± 0.33 mm, respectively). For both body positions, there were no differences in ACD and AL between visit 1 and visit 2. Correlations were strong between the visits, but the limits of agreement varied. Similarly, there were no significant differences between Observer 1 and Observer 2. Correlations and ICC were strong-to-moderate between the observers, and the limits of agreement varied.

Conclusion: Consistent with reports on other a-scan devices, the Scanmate-A measured shorter AL and shallower ACD than the IOLMaster. Although, mean or median AL and ACD did not differ across study visits, observers, and body positions, large limits of agreement on Bland-Altman analyses must be accounted for by users of the Scanmate-A.