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Y. Yasuno, K. Kawana, M. Yamanari, M. Miura, S. Fukuda, T. Oshika; Improved Visualization of Trabecular Meshwork by Polarization Sensitive Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3349.
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© ARVO (1962-2015); The Authors (2016-present)
Anterior eye segment optical coherence tomography (AS-OCT) is an emerging modality for the screening of angle closure glaucoma (ACG). For this screening, a scleral spur (SS) is used as a landmark to assess the angle. On the other hand, trabecular meshwork (TM) is a more direct landmark, because TM is a drainage channel of aqueous humor. However, the location of TM is rarely identified by OCT.Recently developed polarization sensitive AS-OCT (PS-AS-OCT) is known to provide enhanced visualization of tissues, in which TM is appeared as a bended band pattern (figure). However, no evidence has been shown to prove this enhanced visualization. This paper aims at presenting the first evidence based study proving the improved visibility of TM by PS-AS-OCT.
32 eyes of 32 normal subjects were involved. The eyes were scanned by a custom made PS-AS-OCT developed by the authors. This OCT acquires 3D PS-OCT volume within 3.3 sec, and provides not only a conventional OCT (C-OCT), but also a birefringence OCT (B-OCT) volume. 16 cross-sections were created from the C- and B- OCT volumes for 8 radial directions. The visibilities of TM in each section were graded by 3 graders with 4-leveled grading system (1: invisible to 4: clearly visible).
Intraclass correlation analysis showed moderate to high inter-observer correlations of visibility among 3 graders both for B- and P-OCT (rho = .63, .74, .56 for C-OCT, and rho = .59, .72, .48 for P-OCT). Mann-Whitney test showed significant improvement of visibility in B-OCT for all graders (p < .001). The unevenness of the visibility between temporal (T-) and nasal (N-) directions was found by Wilcoxon’s signed rank test. Namely, the visibility in B-OCT is better for N than T, while antithetical tendency was found in P-OCT. This tendency was found for all graders and statistically significant for 1 grader.
PS-OCT provides better visibility of TM and is a promising tool for the screening of ACG. The uneven visibility may indicate the inhomogeneity of optical property of TM.
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