Choroidal Structural Changes in Vogt-Koyanagi-Harada disease after treatment determined by Binarization of EDI-OCT images

Abstract

Purpose: It is well known that the choroidal thickness of Vogt-Koyanagi-Harada syndrome (VKH) in acute phase is thick and decreases quickly with corticosteroid treatment by using enhance depth imaging OCT (EDI-OCT) technique. The choroidal thickness would be certainly the important marker; however, it is not enough to represent every disease condition. Our purpose is to see the structural changes of choroid in the VKH by analyzing the OCT image using binarization technique.

Methods: This study included 32 eyes of 16 patients (2 men and 14 women) with VKH and a retrospective case-series. Choroidal images were recorded by EDI-OCT at baseline and 1 week and 1 month after the initiating steroid therapy. The EDI-OCT image was converted to binarization image by a modified Niblack method by ImageJ (version 1.47; provided in the public domain by the National Institutes of Health, Bethesda, MD, USA; http://imagej.nih.gov/ij/). The luminal area and the stromal area were separately measured and analyzed.

Results: The choroidal area was 472 ± 63 × 10⁴ µm² (stromal area 188 ± 34 ×10⁴ µm² and luminal area 285 ± 32 ×10⁴ µm² ) at baseline, which significantly decreased after the treatment 243 ± 44 ×10⁴ µm² (stromal area 80 ± 13 × 10⁴ µm² and luminal area 163 ± 34 × 10⁴ µm² ) at 1 week (P < 0.01) and 217 ± 47 × 10⁴ µm² (stromal area 73 ± 14 × 10⁴ µm² and luminal area 143 ± 35 ×10⁴ µm² ) at 1 month (P < 0.01). Although both of stromal and luminal areas reduced its size, the reduction rate of stromal area (56.5 ± 7.2 %) was significantly greater than luminal area (42.5 ± 12.6 %) from baseline to 1 week (P < 0.01, Mann-Whitney U test). While, the reduction percentage of luminal area from baseline to 1 month was 48.9 ± 14.5 %, and that of stromal area was 59.7 ± 10.4 %, which was insignificant (P = 0.09).

Conclusions: In the choroid of VKH at very early phase of treatment, the stromal area decreased more than luminal area, subsequently both areas decreased similarly. They may reflect the initial disappearance of stromal edema or infiltrating cells, which was detected by the binarization technique.