Significant role of the choroidal outer layer during recovery from choroidal thickening in Vogt-Koyanagi-Harada disease patients treated with systemic corticosteroids

Background: Which of the choroidal layers suffers the most extensive morphological changes during the course of Vogt-Koyanagi-Harada (VKH) disease is still unknown. The aim of this study was to investigate the relationship between total thickness and the thickness of inner or outer layers in the choroid during systemic corticosteroid therapy in patients with VKH disease. Methods: This retrospective case series included 15 eyes of 10 patients with treatment-naive VKH disease (4 men and 6 women; mean age, 41.4 +/- 14.7 years) received systemic corticosteroid therapy. Whole, inner, and outer choroidal thickness was measured manually at 1 week and at 1 and 3 months after initiation of systemic corticosteroid therapy using enhanced depth imaging optical coherence tomography. The mean thickness values of the layers were compared at each stage. Results: Compared with the 1-week baseline, the mean whole and outer choroidal layer thicknesses were significantly lower at 1 (P = 0.008 and 0.03, respectively) and 3 months (P = 0.008 and 0.02, respectively), whereas the inner layer did not significantly thin. Importantly, there was a significant positive correlation between the rates of change of whole and outer layer thickness from 1 week to 3 months (R = 0.9312, P < 0.0001), but not between the rates of whole and inner layer thickness changes. Conclusions: The thinning of total choroidal thickness observed after treatment with corticosteroids strongly correlated with outer layer thinning, suggesting that the choroidal outer layer is the primary target in acute-stage VKH disease.