To investigate the correlation between choroidal and retinal lesions in eyes with acute Vogt-Koyanagi-Harada disease (VKH) using optical coherence tomography (OCT) by using a new parameter, retinal pigment epithelium (RPE) undulation index, which quantitatively describes choroidal deformations.

Retrospective, observational, cross-sectional study.

Spectral-domain OCT (SD OCT) and swept-source OCT images from a consecutive series of 42 eyes in 22 patients with acute VKH who underwent steroid therapy and 20 healthy eyes in 20 volunteers were analyzed retrospectively. Correlations between best-corrected visual acuity (BCVA), axial length change, and OCT parameters were examined. The RPE undulation index was defined as RPE line length to the total scan length ratio on a foveal-centered scan in the SD OCT image.

Eyes with acute VKH showed increased RPE undulation index, choroidal thickness, and retinal thickness compared to normal subjects, which were reduced following steroidal treatment (P < .0001, P = .0003, and P < .0001, respectively). RPE undulation index was related to choroidal thickness (r = 0.624, P = .0043), retinal thickness (r = 0.483, P = .0028), and BCVA (r = 0.588, P = .0002). Meanwhile, no statistically significant relationship was observed between choroidal thickness and retinal thickness. Axial length changes were significantly correlated with both choroidal thickness (r = 0.842, P < .0001) and RPE undulation index (r = 0.600, P = .0139).

This study demonstrated that the choroid was diffusely undulated and bulged inward in eyes with acute VKH. Correlations between RPE undulation index and choroid morphology, retinal thickness, and poor BCVA suggest that choroidal folding, quantified by RPE undulation index, is useful in assessing VKH disease severity.