Abstract
Purpose: To compare the precision of anterior chamber angle (ACA) and anterior chamber depth (ACD) measurements taken with ultrasound biomicroscopy (UBM) and the Artemis-2 Very High Frequency Ultrasound Scanner (VHFUS) in normal subjects.
Design: Prospective study.
Methods: We randomly selected one eye from each of 59 normal subjects in this study. Two subjects dropped out of the study; the associated data were excluded from analysis. ACA and ACD measurements were obtained using the VHFUS and the UBM. The results were compared statistically using repeated-measures analysis of variance for the intraobserver repeatability, unpaired t-test, and limits of agreement.
Results: The average ACA values for the UBM and the VHFUS (+/- standard deviation) were 41.83 degrees +/- 5.03 degrees and 33.36 degrees +/- 6.03 degrees, respectively. The average ACD values were 2.96 +/- 0.34 mm and 2.87 +/- 0.31 mm. The intraobserver repeatability analysis of variance P-values for ACA and ACD measurements using UBM were 0.10 and 0.68, respectively; for the Artemis-2 VHFUS, the respective values were 0.68 and 0.09. The difference in ACA measurements was statistically significant (t = 8.41; P < 0.0001), while the difference in ACD values was not (t = 1.51; P < 0.13). The mean ACA difference was 8.50 degrees +/- 2.50 degrees, and the limits of agreement were +13.30 degrees to -3.60 degrees. The mean ACD difference was 0.09 +/- 0.27 mm, and the limits of agreement ranged from 0.61 mm to -0.43 mm. The mean difference percentage of ACD was 3.1% for both instruments.
Conclusion: In case of the ACD, both instruments can be used interchangeably; however, with the ACA instruments, they cannot be used interchangeably.