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Shinichi Usui, Yasushi Ikuno, Masahiro Akiba, Nozomu Matsubara, Yuriko Yoshinaga, Tomoko Asai, Atsuya Miki, Kohji Nishida; Peripapillary Tilting Measurement Using Optical Coherence Tomography in Healthy Japanese Eyes. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):592.
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© ARVO (1962-2015); The Authors (2016-present)
We previously reported differing patterns of visual field loss resulting from peripapillary tilting between eyes with highly myopic normal tension glaucoma (NTG) and non-highly myopic NTG. In this study, we evaluated peripapillary tilting in healthy eyes and analyzed parametric reproducibility.
Seventy-nine eyes (43 healthy Japanese subjects; mean age, 45.2±18.5 years; axial length, 23.84±0.98 mm) were enrolled. We used high-penetration optical coherence tomography (OCT) for optic disc imaging. To measure peripapillary tilting, 3.4-, 3.7-, and 4-mm-diameter circular scan images around the optic disc were extracted from 6x6-mm three-dimensional OCT volume images. The retinal pigment epithelial (RPE) line was traced, the image divided into 24 clock hours (Fig 1, superior [S] 1-S12 and inferior [I] 1-I12), and the average RPE line height calculated in each sector (H1). The peripapillary tilting index (PTI) (pixels) (difference in RPE height between one sector and its counterpart) was evaluated (H2). Each sectorial PTI was shown in the central optic disc as 0 pixel. The sector with the minimal PTI (PTImin) indicated the tilting direction. Regarding PTI mapping, the ± degrees between the line with the PTImin and the horizontal line of the optic disc was referred to as peripapillary tilting degrees, theta. The intervisit PTI reproducibility for each diameter of the circular scan image was validated twice on different days based on OCT images from 20 eyes (10 subjects) and intraclass correlation coefficients (ICC) determined.
The average PTI reproducibility with the three diameters was good (ICC, 0.84-0.94) in all sectors. In all eyes, ~86% of the tilting direction was the same among the diameters. The mean PTImin was -314±224 in the 3.4-, -332±224 in 3.7-, and -358±259 in 4-mm-diameter images; theta was -0.47±30.2 in the 3.4-, -0.09±30.7 in 3.7-, and +0.4±30.8 in 4-mm-diameter images. About 80.8~82.2% had tilting in four sectors: S1, 30.3~31.6%; I1, 18.9~26.5%; S2, 12.6~15.1%; and I2, 11.2~15.1% with the three diameters.
PTI reproducibility was good. Each PTI value obtained using the three circular scan diameters was acceptable. The absolute PTImin value enlarged with the larger circular scan diameter. Most healthy Japanese subjects had peripapillary tilting in four sectors. The PTI will be useful to evaluate the morphology of the optic disc complex.
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