Abstract
Purpose
To evaluate the inter- and intra-observer agreement of measurement of the iris–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).
Methods
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. Bland–Altman plots and 95 % limits of agreement (LOA) were reported.
Results
Study subjects were predominantly Chinese (54/60, 90 %) and female (42/60, 70 %), with a mean age of 65.5 years. The median ITC index for eyes with open angles (31/60) and closed angles was 20 % (95 % confidence interval [CI] — 13.6, 27.8) and 49 % (95%CI — 35.5, 69.2) respectively. The mean difference (95 % LOA) for intra-observer agreement for image grading and image acquisition were −0.8 % (−8.2, 6.5) and 0.6 % (−10.9, 9.7); corresponding inter- observer agreement were 0.1 % (−10, 10.1) and −0.3 % (−11.1, 10.5) respectively.
Conclusions
The inter- and intra-observer agreement of the ITC index, as a measure of extent of angle closure using SSOCT, was good.
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None of the authors have any financial/conflicting interests.
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The study was supported by a Translational Clinical Research Program grant, Biomedical Research Council (BMRC), Singapore
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Ho, SW., Baskaran, M., Zheng, C. et al. Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure. Graefes Arch Clin Exp Ophthalmol 251, 1205–1211 (2013). https://doi.org/10.1007/s00417-012-2158-6
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DOI: https://doi.org/10.1007/s00417-012-2158-6