Abstract
BackgroundThe aim was to compare the anterior chamber depth (ACD) measurements taken with Orbscan II, ultrasound biomicroscopy (UBM) and the Artemis-2 VHF (very-high-frequency) ultrasound scanner in normal subjects.MethodsIn this prospective study, one eye from each of 60 normal subjects was randomly selected. Three subjects dropped out of the study because they were apprehensive about the UBM examination; their data were excluded entirely. Measurements of ACD were taken with the Orbscan II, UBM and Artemis-2 VHFUS. Results were obtained for coefficient of variance (CV) and intra-class correlation coefficient (ICC), and statistical analysis was by repeated-measures analysis of variance (ANOVA) for intra-observer repeatability. ANOVA and Bland–Altman analyses were used to determine limits of agreement (LOA) between the three instruments.ResultsThe average ACD (± standard deviation) was 3.13 ± 0.34 mm, 2.96 ± 0.27 mm and 2.87 ± 0.31 mm for the Orbscan II, UBM and Artemis-2 VHFUS, respectively. The repeatability scores were 0.015 ± 0.014%, 0.08 ± 0.09% and 0.07 ± 0.06% for the Orbscan II, UBM and Artemis-2 VHFUS, respectively. The ICC for repeatability of Orbscan II, UBM and Artemis-2 VHFUS measurements was high and equal to 0.99%. The intra-observer repeatability scores of the ACD measurement p-values using Orbscan II, UBM and Artemis-2 VHFUS were 0.12, 0.70 and 0.10, respectively. The mean difference and standard deviations for ACD measurements using Orbscan II vs UBM, Orbscan II vs Artemis-2 VHFUS and UBM vs Artemis-2 VHFUS were 0.17 ± 0.31 mm, 0.27 ± 0.34 mm and 0.10 ± 0.18 mm, respectively. LOAs were 0.78 to -0.44 mm, 0.93 to -0.39 mm and 0.45 to -0.26 mm. ANOVA revealed a statistically significant difference between the Orbscan II, UBM and Artemis-2 VHFUS (p < 0.0001).ConclusionsMeasurements by the three instruments show high repeatability. UBM and the Artemis-2 VHFUS can be used interchangeably, but the Orbscan II cannot be used interchangeably with UBM or the Artemis-2 VHFUS.
Highlights
The aim was to compare the anterior chamber depth (ACD) measurements taken with Orbscan II, ultrasound biomicroscopy (UBM) and the Artemis-2 VHF ultrasound scanner in normal subjects
It is well-documented that anterior chamber depth (ACD) measurement is essential as a screening method for primary angle-closure glaucoma [1,2]; it is used in biometry to calculate the power of intraocular lenses (IOLs) [3], for determining the precise optic zone
Our results show high intra-observer consistency and repeatability of ACD measurements obtained with all three instruments
Summary
The aim was to compare the anterior chamber depth (ACD) measurements taken with Orbscan II, ultrasound biomicroscopy (UBM) and the Artemis-2 VHF (very-high-frequency) ultrasound scanner in normal subjects. It is well-documented that anterior chamber depth (ACD) measurement is essential as a screening method for primary angle-closure glaucoma [1,2]; it is used in biometry to calculate the power of intraocular lenses (IOLs) [3], for determining the precise optic zone. Ultrasound-based methods do not require clear optical media to obtain precise measurements of ACD. There are disadvantages of UBM: for example, the examiner must manually adjust the transducer head to maximize centrality and perpendicularity of the image, which takes time, and analog-based UBM does not image the interface consistently because analog processing does not produce a high enough signal-to-noise ratio between the interface echo complex and the surrounding tissue [13]
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