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Peter Campbell, Rishi Agarwal, Tony Redmond, K Sheng Lim, Bruce Evans; Repeatability and Comparison of Anterior Chamber Angle Assessment Tests. Invest. Ophthalmol. Vis. Sci. 2014;55(13):933.
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To evaluate the repeatability of gonioscopy, van Herick method and Anterior Segment Optical Coherence Tomography (AS-OCT) and assess the agreement between these techniques.
Gonioscopy, van Herick method and AS-OCT were performed on two occasions, one month apart, on patients recruited from optometry practice. All tests were undertaken by one optometrist. One eye was randomly selected for inclusion in the analysis. An eye was graded as occludable with gonioscopy if the posterior pigmented trabecular meshwork was not visible for 90 degrees or more. Anterior Segment images were captured with a Topcon OCT-2000 using the anterior segment setting (see image below). AS-OCT images were graded by a second optometrist masked to the gonioscopy and van Herick method results. The weighted kappa statistic (κ) was used to measure repeatability and agreement.
Results were obtained for 80 eyes of 80 subjects. For gonioscopy, 12 subjects were found to have occludable angles on visit 1 (15%) and 13 subjects on visit 2 (16.2%), κ=0.542. For van Herick method, 17 subjects were found to have occludable angles on visit 1 (21.2%) and 12 subjects on visit 2 (15%) κ=0.641. For AS-OCT, 12 subjects were found to have occludable angles on visit 1 (15%) and 10 subjects on visit 2 (12.5%), κ=0.641. Four subjects had an occludable grading with all three methods at visit 1 and three subjects at visit 2. The agreement between gonioscopy and van Herick was good: κ=0.641 at visit 1 and κ=0.708 at visit 2; agreement between gonioscopy and AS-OCT was fair: κ=0.546 at visit 1 and κ=0.510 at visit 2.
Gonioscopy, despite being a semi-subjective test, is the gold standard method for detecting primary angle closure. Intra-observer repeatability for gonioscopy, van Herick method and AS-OCT is fair, with van Herick method and AS-OCT performing better than gonioscopy. The van Herick method appears to show good agreement with gonioscopy, whereas agreement between AS-OCT and gonioscopy is fair. The van Herick method would appear to be preferable to AS-OCT when considering alternatives to gonioscopy, for example, in glaucoma shared care schemes. OCT instruments that are specifically designed for anterior segment imaging may perform better but are not widely available in clinical practice.
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