Characteristics and reproducibility of anterior chamber angle assessment by anterior-segment optical coherence tomography

Purpose: To evaluate the basic characteristics and reproducibility of anterior chamber angle (ACA) measurements determined by anterior-segment optical coherence tomography (AS-OCT) in open-angle and primary angle closure suspect (PACS) patients. Methods: Thirty-nine open-angle and 18 PACS patients were imaged for ACA by AS-OCT. Subjects underwent imaging of the nasal, temporal and inferior ACA under conditions of constant light, and darkness. For analysis, we used three ACA parameters handled by the Visante OCT software: angle opening distance at 500 mu m (AOD(500)), trabecular-iris space area at 500 mu m (TISA(500)) and angle recess area at 500 mu m (ARA(500)). For determination of inter-session reproducibility, a single well-trained operator (D.Y.K.) scanned all patients at two different visits. For determination of inter-operator variability, a second operator (S. B. P.) acquired another set of images independently. Three sets of images were acquired at least 24 hour apart. Results: All parameters were significantly different when measured both in light and darkness, and in the nasal and temporal quadrants. There were no significant differences between the left and right eyes in the three ACA parameters in all quadrants. The temporal angle was wider than the nasal and inferior angles. All parameters of the nasal, temporal angles had excellent inter-session and inter-operator reproducibility [intra-class correlation coefficient (ICC) 0.796-0.981], but these values were slightly lower for inferior angle measurements (ICC 0.662-0.892) in both open-angle and PACS groups. Conclusion: AS-OCT provides quantitative and reproducible assessment of ACA. Reproducibility was lower in the inferior angle compared with the nasal and temporal angles, perhaps because of variable placement of the scleral spur.