Comparison of anterior chamber depth measurement between Orbscan IIz and ultrasound biomicroscopy

PURPOSE: To compare the measurement of anterior chamber depth exclusive of comeal thickness using Orbscan IIz and ultrasound biomicroscopy (UBM) and evaluate the repeatability of each method. METHODS: Three consecutive measurements of anterior chamber depth were prospectively performed using Orbscan IIz and Paradigm 50-MHz UBM in 40 eyes in 20 individuals. Mean values were compared using the paired t test. For 12 eyes in 6 individuals, anterior chamber depth measurements were performed 5 times to estimate the repeatability of each method by a coefficient of variation. Refractive errors were measured to correlate with anterior chamber depth. RESULTS: The mean anterior chamber depth was 2.82±0.46 mm with the Orbscan IIz and 2.91±0.43 mm in UBM. This difference was statistically significant (P<.001), but not clinically meaningful. The coefficient of variation was 1.15% and 1.10% in Orbscan IIz and UBM, respectively. A negative correlation between anterior chamber depth and spherical equivalent refraction was noted within the range of -5.50 to +3.00 diopters. CONCLUSIONS: The mean anterior chamber depth of Orbscan IIz was 0.087 mm less than that of UBM. Both methods were precise. Orbscan IIz seems to be a useful and more convenient method to measure anterior chamber depth for phakic intraocular lens implantation.