High-Definition Optical Coherence Tomography Imaging of the Iridocorneal Angle of the Eye

Abstract

Anterior segment optical coherence tomography (AS-OCT) uses a 1310-nm diode laser to obtain real-time images of the anterior chamber angle.^1-4 Recent studies have shown that AS-OCT tends to confirm gonioscopic angle closure in most patients but also detects more closed angles than gonioscopy.^5,6 This discrepancy in findings between gonioscopy and AS-OCT may be due to the different anatomical landmarks and levels of irido-angle contact used to define a closed angle. On AS-OCT images, it is not possible to determine the location of the trabecular meshwork, and the presence of any contact between the iris and the angle wall anterior to the scleral spur is graded as angle closure.⁵ However, if this apposition did not reach the level of the posterior trabecular meshwork, the quadrant would be considered open on gonioscopy. Scleral spur determination is impossible in approximately 20% to 30% of AS-OCT images. This could be because of low lateral resolution of AS-OCT images, image artifacts from eyelids or other structures, anatomical variations in eyes, and technical difficulties in imaging some quadrants.⁷ This inability to detect the scleral spur may limit the accuracy and usefulness of angle imaging, especially for quantitative analysis of the angle that uses the scleral spur as an anatomical landmark for measurements.^8,9