Background: Current imaging modalities used in the evaluation of Vogt-Koyanagi-Harada (VKH) disease include ultrasound, fluorescein angiogram, indocyanine green angiography, and optical coherence tomography (OCT). However, they all fail to give detailed information on the ultrastructural changes of the choroid. A recent technique using OCT termed "enhanced depth imaging" produces high-resolution cross-sectional images of the whole thickness of the choroid. The purpose of the study was to describe a novel imaging finding in the choroid in cases of VKH uveitis and to assess for interobserver agreement of this new physical sign.
Methods: This is an age-matched, sex-matched, and spherical equivalent-matched, case-control, cross-sectional study. Six VKH patients in acute and convalescent stages underwent choroidal imaging using enhanced depth imaging spectral-domain OCT imaging. A horizontal enhanced depth imaging spectral-domain OCT scan across the fovea was selected for each eye and was compared with a scan from an age-matched, sex-matched, and spherical equivalent-matched control subject. A loss of focal hyperreflectivity, represented by a decrease in the number of hyperreflective dots in the inner choroid, was observed. This finding was assessed for interobserver agreement using five masked observers. Mean observed agreement and multirater kappa statistics (κ) were calculated. The average choroidal thickness was also calculated and compared among acute-phase VKH patients, convalescent-phase VKH patients, and control subjects.
Results: There was a significant loss of focal hyperreflectivity in the inner choroid of VKH patients compared with control subjects in both acute and convalescent stages. Analysis revealed substantial interobserver agreement on this finding. The mean observed agreement was 95%, and the overall kappa coefficient (κ) was 0.80 (P < 0.01). The choroid of acute-phase VKH patients was thicker than that of convalescent-phase patients by 151 μm (P = 0.043) and control subjects by 137 μm (P = 0.001). There was no statistically significant difference in thickness between convalescent eyes and controls.
Conclusion: Enhanced depth imaging spectral-domain OCT highlights a loss of focal hyperreflectivity in the inner choroid of eyes with VKH, a feature that is consistently observed by independent masked observers. The presence of this feature in both acute and convalescent phases could represent permanent structural change to small choroidal vessels caused by VKH uveitis.