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Hiroshi Yamada, Masanori Hangai, Noriko Nakano, Yugo Kimura, Tadamichi Akagi, Hanako Ohashi Ikeda, Nagahisa Yoshimura; Asymmetry Analysis of Macular Retinal Layers for Diagnosis of Early Glaucoma in Highly Myopic Eyes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):973. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We previously found that asymmetry analysis of the macular inner retinal layers was useful for detecting glaucoma in non-highly myopic eyes. The purpose of this study was to determine whether asymmetry analysis of the macular inner retinal layers would outperform their thickness parameters for detecting early glaucoma in highly myopic eyes.
Twenty nine normal eyes and 33 early glaucomatous eyes of 62 participants were examined. Ten vertical B-scans obtained by SpectralisTM over 30°×15° macular area were manually analyzed for the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), ganglion cell complex (GCC), and total retina (TR) thickness. We calculated an asymmetry index (AI) for each scan for thicknesses of layers in 8 pairs of upper and lower 0.5-mm segments equidistant from the fovea according to the equation AI = |log10 the upper hemi-retina thickness / the lower hemi-retina thickness|. The AI for each eye was the mean of the AIs for that eye’s 10 B-scans.
The average AIs of the TR, GCC, RNFL, and GCL in the normal group were 0.022 ± 0.007, 0.043 ± 0.013, 0.069 ± 0.017, and 0.086 ± 0.016, respectively, whereas those of the early glaucoma group were 0.038 ± 0.013, 0.089 ± 0.037, 0.125 ± 0.052, and 0.157 ± 0.039, respectively (P < 0.001 for all). The average thicknesses of the TR, GCC, RNFL, and GCL in the normal group were 275.9 ± 13.2, 102.3 ± 86.6, 45.4 ± 5.1, and 25.0 ± 3.3, respectively, whereas those of the early glaucoma group were 263.7 ± 12.8, 86.6 ± 9.8, 37.0 ± 8.6, and 19.9 ± 2.5, respectively (P < 0.001 for all). Overlap with normal eyes was less for AIs than for thicknesses of all four layers. The least overlap in values for normal and early glaucomatous eyes was in the AI for the GCL: only 4 (12.1%) of 33 early glaucomatous eyes had AIs that overlapped the normal range. The area under the receiver operating characteristic curves (AROCs) for AI of the TR, RNFL, GCC, and GCL were 0.86, 0.88, 0.92, and 0.98, respectively, whereas that for thickness were 0.75, 0.86, 0.87, and 0.88, respectively. The AROCs for the AIs were higher than those of the thickness between the two groups in all four layers. Significant difference was found between the two groups in only the GCL (P = 0.019).
The GCL asymmetry index outperformed GCL thickness parameters for detecting early glaucoma in highly myopic eyes.
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