title: Choroidal Vascularity Index in Vogt-Koyanagi-Harada Disease: An EDI-OCT Derived Tool for Monitoring Disease Progression.
abstract: OBJECTIVE
  We assessed the application of the choroidal vascularity index (CVI) in the follow-up of Vogt-Koyanagi-Harada disease (VKH) patients derived from image binarization of enhanced depth imaging optical coherence tomography (EDI-OCT) images with Fiji software. Our secondary objective was to derive the retinochoroidal vascularity index based on en face fundus fluorescein and indocyanine green angiography (FFA and ICGA).
  
  
  METHODS
  In this retrospective cohort study, EDI-OCT scans of 18 eyes of 9 patients with VKH were obtained at baseline within 2 weeks of acute presentation, and again at 6 to 12 months. Images with poor quality were excluded. Choroidal thickness (CT) and CVI were analyzed and compared to 13 eyes of 13 healthy controls. En face FFA and ICGA obtained from 12 eyes of 7 patients were segmented to derive retinochoroidal vascularity index.
  
  
  RESULTS
  There was no statistical difference in age or sex between the study group and controls. Choroidal thickness of patients with VKH was 359.23 ± 57.63 μm at baseline, compared to 274.09 ± 56.98 μm in controls (P= 0.003). Follow-up CT in VKH patients was 282.62 ± 42.51 μm, which was significantly decreased from baseline (P= 0.0001). Choroidal vascularity index in VKH patients was 70.03 ± 1.93% at baseline, compared to 64.63 ± 1.92% in controls (P< 0.001). Choroidal vascularity index was 66.94 ± 1.82% at follow-up, significantly reduced from baseline (P< 0.0001). Fundus fluorescein angiography and ICGA retinochoroidal vascularity indices at baseline were 70.67 ± 2.65% and 66.42 ± 2.16%, respectively.
  
  
  CONCLUSIONS
  In this small series of VKH patients, EDI-OCT-derived CVI had a statistically significant reduction over time, similar to CT. We propose that OCT, FFA, and ICGA-derived vascularity indices may be potential novel supportive tools in monitoring disease progression in VKH.
  
  
  CONCLUSIONS
  Choroidal vascularity index can be used potentially to study and analyze the structural changes in choroid. It can be a useful tool to explain the changes in the CT in different retinochoroidal disorders. Choroidal vascularity index also can be used for longitudinal follow-up in patients with VKH disease and other inflammatory disease involving the choroid.
authors.affiliation: National Healthcare Group Eye Institute Tan Tock Seng Hospital, Singapore.
authors.forename: Rupesh
authors.initials: R
authors.lastname: Agrawal
authors.affiliation: National Healthcare Group Eye Institute Tan Tock Seng Hospital, Singapore.
authors.forename: Lilian Koh Hui
authors.initials: LK
authors.lastname: Li
authors.affiliation: Narayana Nethralaya, Bangalore, India.
authors.forename: Vikram
authors.initials: V
authors.lastname: Nakhate
authors.affiliation: National Healthcare Group Eye Institute Tan Tock Seng Hospital, Singapore.
authors.forename: Neha
authors.initials: N
authors.lastname: Khandelwal
authors.affiliation: Narayana Nethralaya, Bangalore, India.
authors.forename: Padmamalini
authors.initials: P
authors.lastname: Mahendradas
keywords: Vogt-Koyanagi-Harada disease; choroid; image analysis; optical coherence tomography