Purchase this article with an account.
R.H. C. Zegers, N.J. Reus, H.G. Lemij; Diagnostic Accuracy of the GDx VCC in the Diagnosis of Glaucoma . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3323.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the diagnostic accuracy of the GDx VCC in the diagnosis of glaucoma. Methods: The GDx VCC, a commercially available scanning laser polarimeter, estimates retinal nerve fiber layer (RNFL) thickness by measuring the summed retardation of a polarized laser beam induced by the birefringent RNFL. The instrument is equipped with automated individualized compensation of anterior segment birefringence. One eye each of 156 patients with primary open–angle glaucoma and 77 age–matched healthy subjects of Caucasian ethnic origin were measured with the GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA, USA). All glaucoma patients had a reproducible glaucomatous visual field defect (mean mean deviation (MD), –8.69 dB) and a glaucomatous appearance of the optic disc in at least one eye. Healthy subjects had normal visual fields (mean MD, 0.39 dB), healthy–looking optic discs, and intraocular pressures ≤21 mmHg in both eyes. We constructed receiver operating characteristic (ROC) curves for the parameters TSNIT Average, Superior Average, Inferior Average, TSNIT SD, and Nerve Fiber Indicator (NFI). At a fixed specificity of 96%, we determined the sensitivity for the best discriminating parameter in the entire group of patients and in patients with mild (mean MD, –2.84 dB), moderate (mean MD, –8.64 dB), and severe (mean MD, –18.46 dB) glaucomatous damage, separately. Results: The areas under the ROC curves (95% confidence interval) for TSNIT Average, Superior Average, Inferior Average, TSNIT SD, and NFI were 0.93 (0.90–0.96), 0.94 (0.91–0.97), 0.90 (0.86–0.94), 0.92 (0.88–0.96), and 0.98 (0.97–1.00), respectively. The NFI, the best discriminating parameter, had an overall sensitivity and specificity of 89% and 96%, respectively, at a cutoff point of ≥40. At this cutoff level, the sensitivities for correctly identifying glaucoma patients with mild, moderate, and severe damage were 85%, 87%, and 100%, respectively. Conclusions: The GDx VCC allowed easy, rapid, and accurate discrimination between healthy and glaucomatous eyes. The NFI was the best discriminating parameter. We think that the GDx VCC fulfills criteria for a glaucoma screening device.
This PDF is available to Subscribers Only