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Published in: Graefe's Archive for Clinical and Experimental Ophthalmology 4/2013

01-04-2013 | Glaucoma

Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure

Authors: Sue-Wei Ho, Mani Baskaran, Ce Zheng, Tin A. Tun, Shamira A. Perera, Arun K. Narayanaswamy, David S. Friedman, Tin Aung

Published in: Graefe's Archive for Clinical and Experimental Ophthalmology | Issue 4/2013

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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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Metadata
Title
Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure
Authors
Sue-Wei Ho
Mani Baskaran
Ce Zheng
Tin A. Tun
Shamira A. Perera
Arun K. Narayanaswamy
David S. Friedman
Tin Aung
Publication date
01-04-2013
Publisher
Springer-Verlag
Published in
Graefe's Archive for Clinical and Experimental Ophthalmology / Issue 4/2013
Print ISSN: 0721-832X
Electronic ISSN: 1435-702X
DOI
https://doi.org/10.1007/s00417-012-2158-6

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