Abstract
AbstractPurpose: To investigate the influence of scan direction on subfoveal choroidal vascularity index (CVI) measurements using spectral‐domain optical coherence tomography (SD‐OCT) in young healthy subjects.Methods: Seventy‐eight eyes of 41 healthy volunteers were included. Choroidal structures were obtained using SD‐OCT with enhanced depth imaging (EDI) through radial scans at the center of the macula at 30° × 30°. The subfoveal choroidal images in the horizontal (0°), 45°, vertical (90°) and −45° directions were recorded and CVIs were analysed according to their respective directions, using image binarization. Additionally, subfoveal choroidal thickness (SFCT) and axial eye length were measured.Results: The SFCT and subfoveal CVI showed a negative correlation but were only significant for the 45° scan (Pearson's r = −0.262, p = 0.021). The axial eye length and subfoveal CVI had no significant correlation in any direction (all p > 0.05). In the Bland–Altman plot, the subfoveal CVI measurement showed high agreement among the four scan directions. When the SFCT was ≥300 μm, there was no difference in the measured values of the subfoveal CVI among the four scan directions; however, when the SFCT was <300 μm, there was a significant difference in subfoveal CVI among the scan directions (one‐way analysis of variance, F = 4.685, p = 0.004).Conclusions: In subfoveal CVI measurement, it is considered that the horizontal (0°) scan can represent the vertical (90°) or oblique (45°, −45°) scans. However, when the SFCT is thinner, the subfoveal CVI in each direction of radial scan may vary significantly. Hence, caution is required in the interpretation.
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