Abstract
Purpose
To compare retinal nerve fiber layer (RNFL) thickness and diagnostic capability of spectral-domain (Cirrus™) versus time-domain (Stratus®) optical coherence tomography (OCT).
Methods
A total of 123 eyes of 123 subjects including 68 normal, 32 glaucoma suspect, and 23 patients with glaucoma were prospectively recruited for the study. All subjects were scanned by Stratus® and Cirrus™ OCT in the same session. Average and quadrant peripapillary RNFL measurements by both machines were correlated using Spearman correlation coefficient, and agreement between testing methods was analyzed by Bland-Altman plots. The area under receiver operating characteristic curves (AUC) for glaucoma diagnosis was calculated.
Results
Average RNFL thickness were significantly thinner on the Cirrus™ compared to the Stratus® OCT in normal subjects and glaucoma suspects (p<0.001), but thicker on the Cirrus™ OCT in glaucoma patients, though the difference was not statistically significant (p=0.53). There was good correlation between the measurements in all 3 groups. In normal controls, the average, superior, nasal, inferior, and temporal correlations were r=0.668, 0.601, 0.508, 0.620, and 0.660, p<0.001, respectively. In glaucomatous eyes, the corresponding values were r=0.560, p=0.005; r=0.423, p=0.04; r=0.117, p=0.596; r=0.742, p<0.001; r=0.669, p<0.001, respectively. The 95% limits of agreement of average RNFL thickness were −30.2 to 13.8 μm. Area under receiver operating characteristic curves for diagnosing glaucoma were comparable (superior RNFL thickness by Cirrus™ 0.925; average RNFL thickness by Stratus® 0.987). Highest correlated AUCs were for inferior and temporal quadrants.
Conclusions
Retinal nerve fiber layer measurements on the Cirrus™ and Stratus® OCT correlate well but do not have clinically acceptable agreement between their measurements. The instruments may not be used interchangeably.
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