Purpose: To study the relationship between retinal nerve fiber layer (RNFL) thickness measured by time domain (Stratus) and spectral domain (Cirrus HD) optical coherence tomography (OCT).
Design: Cross-sectional study.
Participants: Sixty healthy participants, 48 glaucoma suspects, and 55 subjects with glaucoma.
Methods: Participants were imaged by a single trained operator using the Stratus OCT (fast RNFL scan mode) and Cirrus HD-OCT (optic disc cube mode) at the same visit.
Main outcome measures: The RNFL thickness as measured by the Stratus OCT (fast RNFL scan mode) and Cirrus HD-OCT (optic disc cube mode) was compared (paired t test). The relationship between RNFL thickness measurements of the 2 OCTs were evaluated using a Pearson correlation analysis. The presence of abnormal classification, as determined by using an internal normative data base in each machine was compared (chi-square test). The sensitivity and specificity of normative classification of 2 OCT measurements were calculated.
Results: Average RNFL thickness as determined by the 2 OCT machines was correlated (r = 0.94; P<0.001), but was significantly different with the 2 machines (Stratus, 98.0 mum, standard deviation [SD] 18.0; Cirrus, 85.6 mum, SD 14.6; P<0.001). The Cirrus HD-OCT classified a significantly higher percentage of eyes as abnormal (Stratus, 12.9%; Cirrus, 23.3%; P<0.001) in average RNFL thickness. Cirrus OCT demonstrated higher sensitivity and specificity (63.6% and 100%) than Stratus OCT (40.0% and 96.7%) in normative classification of average RNFL thickness.
Conclusions: There were significant differences in RNFL thickness and normative classification as determined by Stratus OCT and Cirrus HD-OCT despite an excellent correlation of RNFL thickness measurement. Overall sensitivity and specificity were higher with Cirrus OCT. These findings are particularly relevant when an individual undergoes longitudinal follow-up with different OCTs.