Anterior Ocular Biometrics as Measured by Ultrasound Biomicroscopy

Abstract

Background: High frequency ultrasonography (ultrasound biomicroscopy; UBM) is an ophthalmic diagnostic tool that can be used to measure the depth of the anterior segment (ASD), the anterior chamber angle (ACA), as well as thicknesses of the iris and the ciliary body (CB). Methods: The anterior segment dimensions and thicknesses were measured by Sonomed 35-MHz. Results: Measurements for 95 eyes from 52 adults were analyzed. The mean and median ASD and ACA were 2.91, 2.92 ± 0.41 mm and 34.1, 34.3 ± 12.1 degrees, respectively. The angle superiorly was wider than inferiorly (p = 0.04). At the root of the iris, the mid of the iris, and the juxtapupillary edge of the iris, the iris thicknesses (median, mean) were 0.40, 0.41 ± 0.1, 0.50, 0.51 ± 0.1, and 0.70, 0.71 ± 0.1 mm, respectively. The thicknesses of CB and CB together with the ciliary processes (median, mean), were 0.70, 0.71 ± 0.15 mm and 1.36, 1.41 ± 0.15 mm, respectively. The upper quadrant of both the iris and the CB was significantly thicker than the lower quadrant (p = 0.04). Conclusions: Our biometric measurements for the anterior segment can be used as normative data for anterior segment depth and angle and iris and ciliary body thickness in normal eyes.