Polarization sensitive optical coherence tomographic documentation of choroidal melanin loss in chronic Vogt-Koyanagi-Harada disease

Abstract

Purpose : We hypothesized that depolarization in polarimetry imaging can reveal levels and distribution of choroidal melanin in normal and pathologic changes affecting the choroid. In this study, we evaluated the sunset glow fundus appearance in chronic Vogt-Koyanagi-Harada (VKH) disease with polarization sensitive optical coherence tomography (PS-OCT).

Methods : We evaluated 26 eyes of 13 patients with chronic VKH disease, 21 eyes of 21 age-matched control subjects and 20 eyes of 20 high myopic subjects with tessellated fundus appearance. Two observers using color fundus images (CF) grouped the eyes with VKH disease either belonging group A (presence of sunset glow fundus) or group B (absence of sunset glow fundus). The presence of melanin in choroid was determined by degree of polarization uniformity (DOPU) obtained by Jones-matrix OCT with 1-µm probing wavelength. Area rate of low DOPU (<0.8) at choroid was calculated with three sets of B-scan images for each case. Sunset grow index [Red/(Red + Green + Blue)] was calculated using mean intensity of each color channel in CF. Classification results with CF by two observers were compared with area rate of low DOPU, sunset grow index, foveal choroidal thickness, standard OCT images, near-infrared images at 780 nm (NIR), and autofluorescence images at 500 nm (SW-AF) and at 780 nm (NIR-AF).

Results : There were 14 eyes in group A and 12 eyes in group B. For all eyes in group A disappearances of choroidal melanin were clearly detected with PS-OCT. Area rates of low DOPU in choroid [ mean ± SD (range)] were 0.004 ± 0.003 (0.0003 - 0.009), 0.26 ± 0.12 (0.09 - 0.48), 0.31 ± 0.12 (0.11 - 0.51) and 0.19 ± 0,.09 (0.10 - 0.42) for group A, B, control group and tessellated fundus group, respectively. Mean area rates of low DOPU in group A was significantly lower than other groups (P < 0.0001), and showed no overlaps with other groups. Distribution of choroidal thicknesses and sunset grow index in group A were substantially overlapped with other groups. Subjective approach of VKH group for group A and B with standard OCT, NIR, SW-AF or NIR-AF showed substantial inconsistencies with CF or PS-OCT.

Conclusions : The PS-OCT provides in-vivo objective evaluation of choroidal melanin loss in sunset grow fundus seen in chronic VKH disease.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.