| Summary: | Purpose: The aim of the study was to evaluate the inter instrument agreement between gonioscopy and anterior segment optical coherence tomography (AS-OCT) in the assessment of the anterior chamber angle (ACA) in eyes with all Van Herick's grades. Methods: A single examiner performed AS-OCT and gonioscopy with a Goldman single mirror for all study patients. An angle opening distance at 500 μm from the scleral spur in the AS-OCT was considered as the quantitative parameter to assess the ACA. A closed ACA on AS-OCT was defined by the presence of any contact between the iris and angle wall anterior to scleral spur. The agreement between gonioscopy and AS-OCT of the nasal and temporal angles was estimated using the Kappa statistic and the concordance between the instruments using the Lin's concordance coefficient. Results: The mean age of the seventy participants in the study was 52.11 ± 5.37 years. Five (15.15%) of nasal angles and 4 (12.12%) of temporal angles identified as closed by gonioscopy were called as open by AS-OCT. The Kappa statistic (0.59), pairwise correlation (0.60), and Lin's concordance correlation coefficient (0.59) showed only moderate agreement and concordance between AS-OCT and gonioscopy. AS-OCT had a moderate sensitivity (73%) and better specificity (86.4%). Conclusion: The results of our study show that AS-OCT can be used as a clinical diagnostic test but has limited use as a screening test for ACA. The significant proportion of subjects with a mismatch in the categorization of open and closed ACA and the moderate agreement highlights the need for better objective diagnostic criteria for closed ACA.
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