PURPOSE: To compare the internal diameter of the anterior chamber among three different imaging modalities: 35-MHz ultrasound biomicroscopy (UBM), Visante optical coherence tomography (OCT), and Pentacam, and to compare the internal diameters with white-towhite (WTW) distance measured by Orbscan. METHODS: The internal horizontal anterior chamber diameter was measured in 20 normal eyes using 35-MHz UBM (Optikon), Visante OCT (Carl Zeiss Meditec), and Pentacam (Oculus Inc). The mean horizontal anterior chamber diameters were compared, and the correlations between each pair of two different methods were evaluated. Horizontal WTW distance was measured by Orbscan IIz (Bausch & Lomb-Orbtek Inc) and then correlated with the measurements of internal anterior chamber diameter. RESULTS: The mean horizontal anterior chamber diameter was 10.99±0.47 mm with UBM, 11.70±0.47 mm with OCT, and 11.86±0.45 mm with Pentacam. Ultrasound biomicroscopy measurements were significantly different than those of OCT and Pentacam (P<.001 for both). However, no significant difference was found between OCT and Pentacam (P=.19). Regarding the correlations between each pair of two different methods, UBM and OCT showed significant correlation (r=0.848, P<.001), but there was no significant correlation between OCT and Pentacam (r=0.403, P=.078), even though the mean values were similar. In the Bland-Altman plots, the range of agreement was 0.51 mm between OCT and UBM, and 0.99 mm between Pentacam and OCT. CONCLUSIONS: Although the internal anterior chamber diameters measured by 35-MHz UBM were significantly smaller than those measured by Visante OCT and Pentacam, the measurements of UBM and Visante OCT showed significant correlation and good agreement with each other. Pentacam showed poor correlation with other measurements.
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