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J. Wahl, L. Barleon, P. Morfeld, S. Haas-Brähler, R. Breitstadt, C. Deters, A. Lichtmeß, B. Brähler, N. Pfeiffer; EDMAGS (Evonik-Degussa-Mainz-Glaucoma Study) III: Development of an Expert System for Glaucoma Screening in the German Chemical Industry. Invest. Ophthalmol. Vis. Sci. 2009;50(13):424.
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© ARVO (1962-2015); The Authors (2016-present)
To generate a glaucoma screening model based on the assessment of the optic disc, the intraocular pressure (IOP) and the visual field (frequency doubling technology, FDT) in a working population.
4234 persons above 40 years working at Evonik Industries were screened using the above mentioned examinations. To minimize observation bias, a glaucoma expert (JW) assessed all optic disc parameters and evaluated all individual screening results in a masked fashion. His diagnosis of glaucoma (no glaucoma, possibly glaucoma, probably glaucoma) was defined as gold standard. The glaucoma screening model took account of the horizontal and vertical cup to disk ratio (CDR), the excavation of the optic disc, optic disc hemorrhage and the distribution of the nerve fibre layer. Asymmetries of CDR and IOP were considered. A glaucoma score was generated by allocating weighted points to each of the parameters. Finally, these points were summed up. The structure of the screening model was specified a priori, whereas parameters were chosen post-hoc to optimize sensitivity and specificity of the algorithm and to yield an almost symmetric distribution of deviations from the gold standard.
16 (0.38%) of the 4234 persons had to be excluded from analysis due to missing FDTs. 98 persons (2.32%) were classified as possible glaucoma patients and 13 (0.31%) as probable glaucoma patients by the expert. Re-evaluation by the screening model revealed a sensitivity of 84% and a specificity of 99% for all glaucoma suspects combined. The positive predictive value of the model was 80.2%, the negative predictive value 99.6%.
Adjustment of optic disc and symmetry parameters with respect to excavation and IOP in an expert model produced sufficiently satisfying sensitivity, specificity and predictive values in comparison to the expert. This screening model seems to be particularly suitable in the working population because of the relatively low age and the low glaucoma prevalence and should be cross-validated in a different study population.
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