Gonioscopy and Ultrasound Biomicroscopy in the Detection of Narrow Anterior Chamber Angle

Abstract

Background: Glaucoma, a leading cause of irreversible blindness worldwide, demands early detection to prevent vision loss. Primary angle-closure glaucoma (PACG) is more common and severe in asian populations. Gonioscopy is the clinical gold standard for evaluating anterior chamber angles (ACA), but its subjective nature limits accuracy. Ultrasound biomicroscopy (UBM) offers an objective, high-resolution alternative. Objective: This study aimed to compare the efficacy of gonioscopy and UBM in evaluating anterior chamber angles in patients with occludable angles identified by van Herick criteria. Methods:  A cross-sectional study was conducted at the National Institute of Ophthalmology & Hospital (NIO&H), Dhaka, from March 2018 to February 2020, involving 30 eyes of 30 patients. Each underwent gonioscopy with a Posner 4-mirror goniolens and UBM using a 50-MHz probe. Parameters measured included Anterior Chamber Angle (ACA), angle opening distance at 500 µm (AOD 500), and anterior chamber depth (ACD). Diagnostic values of UBM were analyzed using SPSS v25. Results: Participants had a mean age of 57.93 ± 6.65 years; 63.3% were female. Gonioscopy mostly revealed Grade 2 angles. UBM commonly showed angles between 110–200 µm. UBM exhibited high sensitivity (91.7%–100%) and specificity (50%–100%), with an overall diagnostic accuracy of 93.3%. Conclusion: UBM is a reliable, sensitive, and specific tool for evaluating occludable angles. It complements gonioscopy and enhances diagnostic precision in glaucoma management, especially in tertiary care settings.