Comparison of Anterior Chamber Depth Measurement Between Orbscan IIz and Ultrasound Biomicroscopy

Abstract

To compare the measurement of anterior chamber depth exclusive of corneal thickness using Orbscan IIz and ultrasound biomicroscopy (UBM) and evaluate the repeatability of each method. 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. 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. 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.