Aims To report the changes of the choroidal structure in the enhanced depth imaging optical coherence tomographic (EDI-OCT) images after high-dose corticosteroid treatment for acute Vogt-Koyanagi-Harada (VKH) disease. Methods Retrospective, observational case series. Thirty-four eyes of 17 patients with acute VKH disease were examined by EDI-OCT before, and 1, 4 and 52weeks after the treatment. The EDI-OCT images were binarised by ImageJ, a publicly accessible software. The luminal, stromal and total choroidal areas and ratio of luminal/stromal area (L/S ratio) were measured in the subfoveal choroid of 1500μm width. The area of the peripapillary atrophy (PPA) was measured in the fundus photographs at 1 and 52weeks. For statistical analyses, a generalised estimating equation method was used to eliminate the effect of within-subject intereye correlations. Results Before treatment, the EDI-OCT images could not be binarised because of poor image quality in most of the cases. After treatment, the luminal, stromal and total choroidal areas were significantly decreased during the follow-up period (all p&lt
0.05). The L/S ratio significantly fluctuated over time (p=0.0201), and was significantly lower at 4weeks than at 1week (p=0.0158). The L/S ratio at 1week was significantly correlated with increase in the PPA area, subsequent chronic recurrences and total dose of corticosteroid (p&lt
0.0001, p=0.0006, p=0.0037, respectively). Conclusions The L/S ratio measured by binarisation of EDI-OCT images was predictive factor for the progression of PPA, subsequent chronic recurrences and total dose of corticosteroid, and may serve as a marker for degree of choroidal inflammation in the VKH disease.