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F. K. Horn, D. Baleanu, C. Y. Mardin, A. M. Juenemann, R. Tornow; Combination of FDT-Perimetry and Nerve Fiber Layer Thickness Measurement With SOCT in Glaucoma Detection. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4396.
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To analyse combined data from frequency doubling technology (FDT) perimetry and retinal nerve fiber thickness measurements with SOCT and to test the diagnostic value of this newly developed classification rule in glaucoma patient groups.
Thickness values of the retinal nerve fiber layer (RNFL) were determined in 32 sectors (11.25° each) using high resolution SOCT (Spectralis, Heidelberg Engineering). For all eyes 16 tracked circular scans around the optic disk (diameter of calculation circles 3.4 mm) were averaged. The thickness of RNFL was automatically segmented using Spectralis software. 175 healthy subjects served as controls to determine age-adjusted confidence limits in 32 sectors. For all individual subjects we generated an "OCT-score" indicating the total length of the individual TSNIT-scan below normal range (in percent). The study included two groups of glaucoma patients of the Erlangen glaucoma registry: 45 patients with "preperimetric" open angle glaucoma (glaucomatous optic disc atrophy and no visual field defect in standard white on white perimetry) and 81 patients with "perimetric" open angle glaucoma (glaucomatous optic disc atrophy and visual field defect in standard perimetry).One eye of each patient and control subject entered the statistical evaluation. All patients had conventional perimetry, evaluation of fundus photographs, SOCT, and FDT screening. FDT evaluation used a published method with casewise calculation of a "FDT-score" including all missed localized probability levels (range 0 to 68). Diagnostic value of procedures has been judged from sensitivity at fixed specificities. In addition to single parameters’ validity, the value of a discriminant function has been calculated for all individuals with the scores delivered by FDT and SOCT.
A combination of FDT perimetry and RNFL measurements yielded better diagnostic results than each of the diagnostic instruments separately. At a pregiven specificity of 97% in our controls, the sensitivity in our patients was:Perimetric glaucoma:SOCT-score= 91%, FDT-score= 91%, combined classifier= 100%.Pre-perimetric glaucoma:SOCT-score= 40%, FDT-score= 39%, combined classifier= 53%.
Combination of different techniques, which include structural and functional methods, is helpful in glaucoma detection.
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