Retinal thickness and volume measurements in diabetic macular edema: a comparison of four optical coherence...

To compare different spectral domain optical coherence tomography devices regarding retinal thickness values in patients with diabetic macular edema and to correlate the results with conventional time domain Stratus OCT data.

Thirty eyes of 30 consecutive patients with diabetic macular edema were included into a prospective study. The macula was examined by Spectralis HRA+OCT, Cirrus HD-OCT, 3D OCT-1000, and Stratus OCT. The procedures' sequence was performed by a single experienced technician in a randomized fashion according to a computer-generated list. In each eye, foveal thickness, foveal volume, and total macular volume were measured automatically. Intraclass correlation, coefficients of variance, and coefficients of repeatability were calculated.

Foveal thickness differed between the particular devices with a mean ± SD ranging from 359.97 ± 105.84 μm to 437.70 ± 115.84 μm. Correlation between the different OCT devices resulted in r > 0.7 (Pearson), and intraclass correlation was >0.9. Agreement of measurements was assessed showing a mean difference of foveal thickness values ranging from 19.2 μm to 77.7 μm (P < 0.05) and coefficients of repeatability ranging from 37.7 μm to 87.4 μm.

While intradevice reproducibility is satisfactory, retinal thickness and volume measurements should not be used interchangeably because measurements differed significantly between systems. The lack of interdevice agreement seems to be related to the different segmentation algorithm of thickness measurement and should be considered because it may strongly influence treatment decisions and conclusions.