Retinal nerve fiber layer analysis with GDxTM: diagnostic value in primary open angle glaucoma and glaucoma suspects

Purpose: to analyze the diagnostic power of the GDx™ Scanning Laser System in primary open angle glaucoma (POAG) and glaucoma suspects. Methods: 77 POAG patients (142 eyes) with characteristic visual field loss, 40 normal subjects and 36 glaucoma suspects (72 eyes) with intraocular pressure (IOP) above 20 and below 25 mmHg with normal visual fields were submitted to GDx™ Scanning Laser System examinations. Sensitivity, specificity, likelihood ratio and pre- and post-test probabilities were calculated. Results: Considering abnormal the presence of at least one parameter out of normal limits, 82.5% specificity and 90.1% of sensitivity between glaucomatous and normals were found. Likelihood ratio was 5.1 and pre-test and post-test probabilities were 63.9% and 90% respectively. Between suspects and normals specificity was 82.5% and sensitivity 33.3%. Likelihood ratio was 1.9 and pretest and post-test probabilities were 8.5% and 15% respectively. Conclusion: The GDx™ Scanning Laser System presented significant diagnostic power to differentiate glaucomatous from normal eyes. The examination showed low performance to differentiate glaucoma suspects from normals.

Nerve fibers; Retina; Glaucoma; Glaucoma; open angle; Sensibility and specificity; Diagnostic techniques; ophthalmological

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