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Shinichi Usui, Yasushi Ikuno, Tsutomu Kikawa, Masahiro Akiba, Tomoko Asai, Atsuya Miki, Kenji Matsushita, Kohji Nishida; Peripapillary tilting predicts pattern of central vision loss in normal tension glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4029.
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© ARVO (1962-2015); The Authors (2016-present)
Myopic glaucoma patients have a high risk of central visual loss. The pathogenesis of the central defects is deep structural deformation by ocular expansion in some myopic eyes. To quantify disc tilting in glaucomatous eyes, we studied the relation between peripapillary tilting by optical coherence tomography (OCT) and vision loss in highly and non-highly myopic normal tension glaucoma (NTG).
In this retrospective observational study, 162 NTG eyes were enrolled:highly myopic NTG group (axial length, AL≧26 mm) and non-highly myopic NTG group (AL<26 mm). High-penetration OCT (DRI-OCT1, Topcon, Japan) was used for optic disc imaging. 1. To measure disc tilting, a 4-mm-diameter circle scan image around the optic disc was extracted from the 6x6-mm 3D OCT volume image. The retinal pigment epithelium (RPE) line was traced, the image divided into 24 clock hours (Fig1, S1-S12 and I1-I12), and the average RPE line height in each sector calculated. 2. The peripapillary tilting index (PTI, pixels), i.e., the difference in RPE height between one sector and its counterpart, was evaluated. 3. The PTI of each sector was shown in the central optic disc as 0 pixel. The sector with minimal PTI (PTImin) shows the tilting direction. 4. PTI mapping. The ± degree between the tilting line with PTImin and the horizontal line of the optic disc was named the tilting degree, theta. The relation between tilting sectors and the visual field was evaluated. Threshold values of 4 paracentral points within 5° on the SITA30-2 test were used to evaluate central vision loss. The Tukey-Kramer multiple comparison test was used for statistical comparisons. Difference tests for multiple comparisons were considered significant at P<0.05.
Eighty-one eyes were in each study group. In all NTG eyes, ~71% had tilting in 3 sectors: 34.5% in I1, 22.4% in I2 and 13.5% in S1 (Fig.2). Multiple comparisons of paracentral vision loss among those sectors found that highly myopic NTG with S1 and I1 tilting had significant inferior paracentral loss; non highly myopic NTG with S1 tilting had significant superior paracentral loss. The S1 mean deviation (-12.5±8.0 db) was significantly worse than I2 (-6.8±6.0 db) in highly myopic NTG.
The patterns of paracentral vision loss by peripapillary tilting differ between the two study groups. Deep structural optic disc changes may be affected by disc tilting in highly myopic eyes.
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