Diagnostic ability of Fourier-domain vs time-domain optical coherence tomography for glaucoma detection

Abstract

Purpose: To compare retinal nerve fiber layer (RNFL) thickness assessments and the discriminating ability of Fourier-domain optical coherence tomography (FD-OCT) with that of time-domain optical coherence tomography (TD-OCT) for glaucoma detection.

Design: Prospective, nonrandomized, observational cohort study.

Methods: Normal and glaucomatous eyes underwent complete examination, standard automated perimetry, optic disc photography, TD-OCT (Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA), and FD-OCT (RTVue; Optovue Inc, Fremont, California, USA). One eye per subject was enrolled. Two consecutive scans were acquired using a 3.46-mm diameter scan with TD-OCT and a 3.45-mm diameter scan with FD-OCT. For each of 5 RNFL parameters, the area under the receiver operator characteristic curve was calculated to compare the ability of FD-OCT and TD-OCT to discriminate between normal and glaucomatous eyes.

Results: Fifty healthy persons (mean age, 65.3 +/- 9.9 years) and 50 glaucoma patients (mean age, 67.7 +/- 10.5 years) were enrolled. Average, superior, and inferior RNFL thickness measurements (in micrometers) were significantly (P < .01) greater with FD-OCT compared with TD-OCT in normal eyes (103.3 +/- 12.6 vs 96.3 +/- 10.7, 134.5 +/- 18.6 vs 113.9 +/- 16.3, and 129.7 +/- 16.9 vs 125.5 +/- 15.8, respectively) and glaucomatous eyes (P < .001; 77.6 +/- 17.6 vs 70.4 +/- 18.6, 108.0 +/- 26.8 vs 86.8 +/- 30.2, 82.2 +/- 3.3 vs 73.5 +/- 26.1, respectively). The area under the receiver operator characteristic curves for RNFL thickness were similar (P > .05) using FD-OCT (average, 0.88; superior, 0.80; inferior, 0.94) and TD-OCT (average, 0.87; superior, 0.79; inferior, 0.95).

Conclusions: Cross-sectional peripapillary RNFL thickness measurements obtained using FD-OCT generated with the RTVue are greater than those obtained with TD-OCT and have similar diagnostic performance for glaucoma detection.

Figure 1

illustrates an optic disc photograph (top left) of a right eye with advanced glaucomatous optic neuropathy and diffuse thinning of the neural rim, and corresponding double arcuate scotoma (top right) using standard automated perimetry. Time-domain (bottom left) and Fourier-domain (bottom right) optical coherence tomography images demonstrate diffuse thinning of the RNFL (average thickness 47.25μ and 48μ, respectively), outside 95% confidence limits of age-matched normal subjects. Note that 90-degree quadrantic RNFL assessments using TD-OCT (64 A-scans/quadrant) were generated using an average of three segments; corresponding 90-degree quadrantic RNFL assessments using FD-OCT (250 A-scans/quadrant) were generated using an average of four segments.

Figure 2

demonstrates the area under the receiver operator characteristic curves (AUROC) for the best parameter obtained using time-domain optical coherence tomography (inferior RNFL thickness, AUROC = 0.95) and Fourier-domain optical coherence tomography (inferior RNFL thickness, AUROC = 0.94, p = 0.45).