Macular and retinal nerve fiber layer thickness measurements in normal eyes with the Stratus OCT, the Cirrus HD-OCT, and the Topcon 3D OCT-1000.

Purpose

To compare retinal nerve fiber layer (RNFL) and macular thickness measurements using time-domain optical coherence tomography (TD OCT) and 2 Fourier-domain OCTs (FD OCT).

Methods

Sixty eyes of 60 normal participants underwent eye examination followed by OCT evaluation with the time-domain Stratus OCT (Carl Zeiss Meditec, Inc. Dublin, CA) and 2 FD OCTs-the Cirrus HD-OCT (Carl Zeiss Meditec, Inc. Dublin, CA) and the 3D OCT-1000 (Topcon Corporation, Tokyo, Japan). Each patient was scanned 3 times on each machine by the same physician examiner. RNFL and macular thickness measurements were compared across the 3 devices using repeated measures analysis of variance (ANOVA) and multiple comparison t tests with Bonferroni adjustments. The coefficients of variation (CV) and the intraclass correlation coefficients were calculated to assess reproducibility. Bland-Altman plots were constructed to assess the level of agreement between every 2 OCTs.

Results

All 3 machines revealed similar patterns of regional differences in RNFL and macular thicknesses. Macular thickness was consistently greatest on the Cirrus and lowest on the Stratus device. However, RNFL measurements were less consistent. The overall average RNFL thickness was 4 μm greater on the Stratus than on the 3D OCT-1000, which was in turn 5 μm greater than on the Cirrus device. Bland-Altman plots showed poor-to-moderate agreement in terms of macular and RNFL thickness measurements between each 2 of the OCT devices. Both FD OCTs provided more reproducible readings on macular measurements than the Stratus, as evidenced by the lower CV and higher intraclass correlation coefficients. However, RNFL measurements on the 2 FD OCTs were not necessarily more reproducible than those from the Stratus OCT.

Conclusion

Thickness measurements are not interchangeable among different OCT devices because of the poor-to-moderate interdevice measurement agreement. FD instruments yield more reproducible macular but not RNFL thickness measurements.