Automatic detection of schwalbe's line in the anterior chamber angle of the eye using HD-OCT images

Angle-closure glaucoma is a major cause of blindness in Asia and could be detected by measuring the anterior chamber angle (ACA) using gonioscopy, ultrasound biomicroscopy or anterior segment (AS) optical coherence tomography (OCT). The current software in the VisanteTM OCT system by Zeiss is based on manual labeling of the scleral spur, cornea and iris and is a tedious process for ophthalmologists. Furthermore, the scleral spur can not be identified in about 20% to 30% of OCT images and thus measurements of the ACA are not reliable. However, high definition (HD) OCT has identified a more consistent landmark: Schwalbe's line. This paper presents a novel algorithm which automatically detects Schwalbe's line in HD-OCT scans. The average deviation between the values detected using our algorithm and those labeled by the ophthalmologist is less than 0.5% and 0.35% in the horizontal and vertical image dimension, respectively. Furthermore, we propose a new measurement to quantify ACA which is defined as Schwalbe's line bounded area (SLBA).