Diagnostic ability of Cirrus anterior segment optical coherence tomography to differentiate between binary grades of narrow angles seen on gonioscopy

Purpose: To assess diagnostic performance of Cirrus Anterior Segment Optical Coherence Tomography (ASOCT) parameters to differentiate gonioscopic grades of narrow angles. Methods: This prospective cross sectional study included 100 eyes with clinically diagnosed angle closure disease. Quantitative ASOCT parameters such as angle width, angle opening distance (AOD), trabecular iris space area (TISA) at scleral spur distances of 500 and 750µm were measured.Shaffer’s grading system was used to grade narrow angles. Area under the receiver operating characteristic curves (AUCs) were generated to assess diagnostic performance of these measurements to differentiate grades of narrow angles. Results: 68 eyes were available for analysis. . Correlation between grade 0/1 on gonioscopy with 0–10° on ASOCT was seen in 81.3% of eyes in the nasal angle and 76.1% of eyes in the temporal angle ( P < 0.001), and grade 2 angle with 11–20° on ASOCT was seen in 80.0% of eyes in the nasal angle and 72.7% eyes in temporal angle ( P < 0.001). AUC for grade 0/1 and grade 2 angles on gonioscopy was highest for AOD500 nasally (0.80 [95% confidence interval (CI), 0.68–0.88]) while temporally, it was highest for TISA500 (0.72 [95% CI, 0.60–0.82]). Kappa coefficient between gonioscopy vs ASOCT was found to be 0.57 (95% CI, 0.36–0.75) nasally and 0.46 (95% CI, 0.24–0.67) temporally. Conclusion: Discrimination capability of ASOCT parameters appears to be limited for differentiating between various grades of narrow angle. Further studies with larger sample sizes are required to study the utility of ASOCT in this aspect.