Anterior segment biometry using ultrasound biomicroscopy and the Artemis-2 very high frequency ultrasound scanner

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° ± 5.03° and 33.36° ± 6.03°, 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° ± 2.50°, and the limits of agreement were +13.30° to -3.60°. 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.

Keywords: Artemis-2 VHF scanner; anterior chamber angle; anterior chamber depth; normal eyes; ultrasound biomicroscope.

Figure 1

The image was obtained for one of the subjects with Artemis-2 VHFUS for ACA and ACD. A black and white, and B in color. Abbreviations: VHFUS, very high frequency ultrasound scanner; ACA, anterior chamber angle; ACD, anterior chamber depth.

Figure 2

The image was obtained for the same subject but with UBM for ACA and ACD. A black and white, and B in color. Abbreviations: UBM, ultrasound biomicroscopy; ACA, anterior chamber angle; ACD, anterior chamber depth.

Figure 3

Bland–Altman diagram showing the difference and agreement limits of the ACA measurements obtained with UBM and the Artemis-2 VHFUS. Abbreviations: ACA, anterior chamber angle; UBM, ultrasound biomicroscopy; VHFUS, very high frequency ultrasound scanner.

Figure 4

Bland–Altman diagram showing the difference and agreement limits of the ACD measurements obtained with the UBM and Artemis-2 VHFUS. Abbreviations: ACD, anterior chamber depth; UBM, ultrasound biomicroscopy; VHFUS, very high frequency ultrasound; SD, standard deviation.