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Masaki Tanito, Koji Nitta, Maki Katai, Yasushi Kitaoka, Yu Yokoyama, Kazuko Omodaka, Satoru Tsuda, Toshiaki Nakagawa, Toru Nakazawa, The Glaucoma Stereo Analysis Study Group; Discrimination of glaucomatous optic disc with different appearances by using optic disc morphology parameters - The Glaucoma Stereo Analysis Study (GSAS). Invest. Ophthalmol. Vis. Sci. 2014;55(13):4779.
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© ARVO (1962-2015); The Authors (2016-present)
The Glaucoma Stereo Analysis Study (GSAS) is a multicenter, collaborative study to explore characteristics of glaucomatous optic disc morphology by using a stereo fundus camera. Using optic disc parameters obtained from GSAS, the equations that discriminate subjectively classified different optic disc appearances were objectively established.
The GSAS enrolled study criteria-eligible 187 primary open angle glaucoma eyes from 187 subjects (100 males, and 87 females, mean ± SD age of 62 ± 9 years). Optic discs recorded by stereo fundus camera (nonmyd WX, Kowa Company Ltd., Japan) were three-dimensionally analyzed by newly developed software to calculate various optic disc parameters. Based on the proposal by Nicolela and Drance (Ophthalmology 103(4), 640-9, 1996), three independent graders classified each optic disc appearance into 4 subclasses [focal ischemic, FI (n=34); myopic glaucomatous, MY (n=96); senile sclerotic, SS (n=19); and generalized enlargement, GE (n=38)]. To obtain equations to calculate probability of these 4 subclasses, all 38 optic disc parameters-substituted discrimination analyses with a stepwise forward selection method were performed.
By the analyses, 6 parameters including temporal rim-to-disc ratio average, nasal rim-to-disc ratio average, mean cup depth, rim decentering absolute, height variation contour, and horizontal disc tilt angle were included in the equations; area under the receiver operating characteristic curves for discrimination of 4 subclasses by using established equations were calculated to be 0.88, 0.93, 0.86, and 0.91 for FI, MY, SS, and GE, respectively. Based on the probability assessment, the eyes were re-classified into 118 (63%) single subclass type (>60% probability for either subclass), 30 (16%) mixed type (>60% probability for either top 2 subclasses), and 39 (21%) unclassified type optic discs.
The equations derived from stereo fundus camera analyses enable quantification of each component of different optic disc appearances in each eye and can provide a novel parameter to describe glaucomatous optic disc head characteristics.
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