Comparisons of Choroidal Thickness of Normal Eyes Obtained by Two Different Spectral-Domain OCT Instruments and One Swept-Source OCT Instrument

PURPOSE: We compared the subfoveal choroidal thickness (SFCT) measured on the images obtained by two spectral-domain optical coherence tomographic (SD-OCT) instruments and one swept-source OCT (SS-OCT) instrument. METHODS: A cross-sectional, prospective noninterventional study was done in which SFCT was measured in the images obtained by two SD-OCT instruments; Heidelberg Spectralis-OCT (Spectralis-SD-OCT) and Topcon 3D OCT-1000 Mark II (Topcon-SD-OCT). Images also were obtained with SS-OCT Atlantis DRI OCT-1 (DRI-SS-OCT). After manual segmentation, the measurements were made using the calipers embedded in each instrument. The intrarater, interrater, and intermachine agreements were assessed. RESULTS: We studied 35 subjects. The intrarater correlation coefficient (95% confidence interval) was 0.994 (0.988-0.994) for Spectralis-SD-OCT, 0.996 (0.993-0.998) for Topcon-SD-OCT, and 0.997 (0.991-0.998) for DRI-SS-OCT (P < 0.001). The interrater correlation coefficient was 0.995 (0.991-0.998) for Spectralis-SD-OCT, 0.995 (0.990-0.998) for Topcon-SD-OCT, and 0.996 (0.992-0.998) for DRI-SS-OCT (P < 0.001). The average SFCT was 273.2 μm with Spectralis-SD-OCT, 269.1 μm with the Topcon-SD-OCT, and 280.5 μm with DRI-SS-OCT. The intermachine correlation coefficient was 0.982 (0.964-0.991) for Spectralis-SD-OCT versus Topcon-SD-OCT, 0.907 (0.815-0.953) for Topcon-SD-OCT versus DRI-SS-OCT, and 0.911 (0.832-0.954) for DRI-SS-OCT versus Spectralis-SD-OCT (P < 0.001). The SFCT measured with DRI-SS-OCT was significantly thicker than that with Topcon-SD-OCT, with a mean difference of 11.41 ± 30.27 μm (P = 0.032). CONCLUSIONS: In normal adult eyes, there was good reproducibility and repeatability of SFCT measurements obtained by the SD-OCT and SS-OCT instruments. However, the choroid measured with DRI-SS-OCT was thicker than that measured with both SD-OCT instruments, and, thus, the choroidal thickness should not be compared between the SD-OCT and SS-OCT instruments. (www.umin.ac.jp/ctr number, UMIN000011259.).