A New Optical Coherence Tomography Method for Subfoveal Choroidal Thickness Measurement: A Single-center Observational Study

Background: Several macular pathologies are associated with choroidal vascular supply, and thus require choroidal thickness evaluation. However, there is no standard subfoveal choroidal thickness (SFCT) measuring method. This study investigated a new method to measure the SFCT, using optical coherence tomography. Methods: This is a single-center observational study. Eighty-two senior medical students participated as observers and independently measured the SFCT on five standard optical coherence tomography images of healthy adults in a tertiary care setting. They used three different methods: (1) the observer’s own method, (2) the conventional method, perpendicular to the retinal pigment epithelium, and (3) the new method, along a virtual line connecting the umbo with the most elevated point of the ellipsoid. Additionally, the SFCT angle—the angle between the measurement line and the vertical line of the image—was measured and compared between methods. The intraclass correlation coefficient was used to determine interpersonal variability. Results: The intraclass correlation coefficients for SFCT measured by methods 1, 2, and 3 were 0.853, 0.880, and 0.896, respectively ( P < 0.001 for all). It was the highest with method 3; the intraclass correlation coefficients SFCT angles were 0.647, 0.842, and 0.307, respectively ( P < 0.001 for all). Conclusions: The new method showed the lowest interpersonal variability, and could therefore be a reliable standard for SFCT measurement, even in foveae with a steep slope on optical coherence tomography. Trial registration Not applicable