Effect of spectrum bias on the diagnostic accuracy of spectral-domain optical coherence tomography in glaucoma

Abstract

Purpose: To evaluate the influence of a control group on the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) in early glaucoma.

Methods: In a diagnostic, case-control study, 119 eyes of 60 normal subjects with no findings suspicious for glaucoma (control cohort 1); 76 eyes of 41 subjects referred by general ophthalmologists as glaucoma suspects based on optic disc morphology, but found by glaucoma experts to be normal but with physiological variations in their optic nerves (control cohort 2); and 65 eyes of 46 early-glaucoma patients (cases) underwent imaging of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) by SD-OCT.

Results: Areas under the receiver operating characteristic curves (AUC) of ONH parameters discriminating glaucomatous eyes from normal eyes of control cohort 2 were significantly lesser (P < 0.001) than those discriminating glaucomatous eyes from normal eyes of control cohort 1. AUCs of RNFL parameters discriminating glaucomatous eyes from normal eyes of control cohorts 2 and 1 were comparable. Although the AUCs of GCC thickness parameters were comparable, AUCs of GCC focal and global loss volume in control cohort 2 (0.684 and 0.671. respectively) were significantly less (P < 0.05) than in control cohort 1 (0.881 and 0.841, respectively).

Conclusions: The effectiveness of most SD-OCT parameters in detecting glaucoma significantly decreased when evaluated against a clinically relevant control group with suspicious-looking optic nerves compared with that against a control group consisting of normal subjects with no findings suspicious for glaucoma.