Study of anterior chamber angle: Gonioscopy and ultrasound biomicroscopy

Gonioscopy is the widely used technique of grading and evaluating the anterior chamber angle in current glaucoma evaluation practice. The grading of angle and open angle or narrow angle classification with gonioscopy is fairly accurate when done by an experienced ophthalmologist. In recent years, UBM and anterior segment OCT are advanced and in depth imaging tools for the anterior segment evaluation and accurate angle measurements. In our study, we have included 200 eyes for anterior chamber angle grading with gonioscopy and UBM and results are compared. Our study shows that some amount of estimation of angle depth by gonioscopy is overestimated in nearly closed and grade 1 angles. Estimation of grades 2 and 3 is nearly accurate with gonioscopy and comparable to UBM angle grading. Over diagnosis of occludable angles with gonioscopy which can be explained due to iris contour, inter-observer reliability or limitation to examine far periphery of the angle and this can be overcome by UBM examination. UBM provides accurate anterior chamber angle in degrees, peripheral iris configuration details and quantification of measurements is possible. Keywords: Gonioscopy, Ultrasound Biomicroscopy (UBM).