Swept source optical coherence tomography measurement of the irisâ[euro]"trabecular contact (ITC) index: a new parameter for angle closure

• Published in: Graefe's archive for clinical and experimental ophthalmology 2013-04, Vol.251 (4), p.1205
• Main Authors: Ho, Sue-wei, Baskaran, Mani, Zheng, Ce, Tun, Tin A, Perera, Shamira A, Narayanaswamy, Arun K, Friedman, David S, Aung, Tin
• Format: Article
• Language: English
• Subjects: Ophthalmology
• ISSN: 0721-832X; 1435-702X
• DOI: 10.1007/s00417-012-2158-6

To evaluate the inter- and intra-observer agreement of measurement of the irisâ[euro]"trabecular contact (ITC) index, a measure of the degree of angle closure, using swept source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan). One randomly selected eye of 60 subjects was imaged under dark room conditions. The SSOCT 3-dimensional angle scan simultaneously obtains 128 radial scans of the anterior chamber for the entire circumference of the angle. Post-imaging analysis estimated the ITC index using in-built software. For intra-observer agreement for image grading, one examiner performed the grading twice in a masked fashion and random order after a 1-week interval. A second examiner graded images to assess inter-observer agreement for image grading. For intra-observer agreement for image acquisition, a single operator imaged patients twice. For inter-observer agreement for image acquisition, a single observer graded two sets of images acquired by two different operators on the same patient. Blandâ[euro]"Altman plots and 95Â % limits of agreement (LOA) were reported. Study subjects were predominantly Chinese (54/60, 90Â %) and female (42/60, 70Â %), with a mean age of 65.5Â years. The median ITC index for eyes with open angles (31/60) and closed angles was 20Â % (95Â % confidence interval [CI] â[euro]" 13.6, 27.8) and 49Â % (95%CI â[euro]" 35.5, 69.2) respectively. The mean difference (95Â % LOA) for intra-observer agreement for image grading and image acquisition were â '0.8Â % (â '8.2, 6.5) and 0.6Â % (â '10.9, 9.7); corresponding inter- observer agreement were 0.1Â % (â '10, 10.1) and â '0.3Â % (â '11.1, 10.5) respectively. The inter- and intra-observer agreement of the ITC index, as a measure of extent of angle closure using SSOCT, was good.[PUBLICATION ABSTRACT]