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L. M. Alencar, M. Balasubramaniam, C. Bowd, R. N. Weinreb, L. M. Zangwill, P. A. Sample, F. A. Medeiros; Comparison of the GDx GPA and the HRT TCA for Detection of Glaucomatous Progression. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4011.
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To evaluate the abilities of the GDx Guided Progression Analysis (GDx GPA) and the HRT Topographic Change Analysis (HRT TCA) to discriminate between stable eyes and eyes with glaucomatous progression determined using standard automated perimetry (SAP) and optic disc stereophotographs.
We included 312 eyes of 202 individuals followed for an average of 4.04±1.15 years enrolled in the longitudinal Diagnostic Innovations in Glaucoma Study (DIGS). At baseline, 77 (25%) eyes had glaucoma with repeatable abnormal SAP, 202 (65%) were suspects (optic disc appearance and/or elevated intraocular pressure) and 33 (11%) were healthy. Visual field progression was evaluated by SAP Guided Progression Analysis. Optic disc progression was evaluated by masked assessment of serial stereophotographs. Progression by the HRT was evaluated using the TCA software conservative criterion (cluster of >= 2% of the disc area and depth of >=100µm). Progression by the GDx was evaluated using Variable Corneal Compensation (VCC) and the Fast Mode of the GDx GPA software.
During follow-up, 42 eyes (14%) progressed by stereophotographs and/or SAP. The GDx GPA detected 17 of these eyes (sensitivity 41%, positive likelihood ratio [LR] 6.9) and the HRT TCA detected 11 (sensitivity 26%, positive LR 2.6). Fourteen eyes showed progression only by the GDx (specificity for correctly classifying no progression in glaucomatous and suspect eyes 94%, negative LR 0.6), and 24 eyes showed progression only by the HRT (specificity 90%, negative LR 0.8). The GDx classified 2 healthy eyes as progressed (specificity for correctly classifying no progression in healthy eyes 94%), and the HRT classified none (specificity 100%). Comparison of the two tests showed no statistically significant difference (McNemar test, P=0.684).
The GDx GPA and the HRT TCA were able to detect glaucomatous progression in a significant number of cases showing progression by conventional methods. Their high specificities suggest that these tests could be used as complementary tools for evaluation of change in glaucoma.
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