Objective evaluation of choroidal melanin loss in patients with Vogt-Koyanagi-Harada disease using polarization-sensitive optical coherence tomography

Polarization-artifact reduction and accuracy improvement of Jones-matrix polarization-sensitive optical coherence tomography by multi-focus-averaging based multiple scattering reduction

Polarization-sensitive optical coherence tomography (PS-OCT) is a promising biomedical imaging tool for the differentiation of various tissue properties. However, the presence of multiple-scattering (MS) signals can degrade the quantitative polarization measurement accuracy. We demonstrate a method to reduce MS signals and increase the measurement accuracy of Jones matrix PS-OCT. This method suppresses MS signals by averaging multiple Jones matrix volumes measured using different focal positions. The MS signals are decorrelated among the volumes by focus position modulation and are thus reduced by averaging. However, the single scattering signals are kept consistent among the focus-modulated volumes by computational refocusing. We validated the proposed method using a scattering phantom and a postmortem medaka fish. The results showed reduced artifacts in birefringence and degree-of-polarization uniformity measurements, particularly in deeper regions in the samples. This method offers a practical solution to mitigate MS-induced artifacts in PS-OCT imaging and improves quantitative polarization measurement accuracy.

Synthesizing the degree of polarization uniformity from non-polarization-sensitive optical coherence tomography signals using a neural network

Degree of polarization uniformity (DOPU) imaging obtained by polarization-sensitive optical coherence tomography (PS-OCT) has the potential to provide biomarkers for retinal diseases. It highlights abnormalities in the retinal pigment epithelium that are not always clear in the OCT intensity images. However, a PS-OCT system is more complicated than conventional OCT. We present a neural-network-based approach to estimate the DOPU from standard OCT images. DOPU images were used to train a neural network to synthesize the DOPU from single-polarization-component OCT intensity images. DOPU images were then synthesized by the neural network, and the clinical findings from ground truth DOPU and synthesized DOPU were compared. There is a good agreement in the findings for RPE abnormalities: recall was 0.869 and precision was 0.920 for 20 cases with retinal diseases. In five cases of healthy volunteers, no abnormalities were found in either the synthesized or ground truth DOPU images. The proposed neural-network-based DOPU synthesis method demonstrates the potential of extending the features of retinal non-PS OCT.

Correlation Between Hyperreflective Foci in the Choroid and Choroidal Discoloration in Vogt-Koyanagi-Harada Disease

Purpose

To investigate the distribution of hyperreflective choroidal foci (HCF) in eyes with Vogt-Koyanagi-Harada (VKH) disease.

Methods

We included 22 eyes of 11 patients with VKH disease in the convalescent stages and 22 eyes of age- and sex-matched normal controls. HCF were quantified using en face optical coherence tomography (OCT) images of the choroid, and the degree of fundus pigmentation was determined by the color balance of the fundus photographs. The results were then analyzed between the eyes with and without sunset glow fundus (SGF).

Results

The median age of patients with VKH disease was 58.0 (range 54.0–65.0) years, and median disease duration was 66.4 (range 8.5–147.7) months. In 22 eyes with VKH, the number and total area of HCF were correlated with the degree of fundus pigmentation (ρ = −0.671, P < 0.001; ρ = −0.612, P = 0.002, respectively). The number of HCF was significantly smaller in VKH disease–affected eyes with SGF (median, interquartile range; 134.6, 110.0–159.2) than in those without SGF (229.0, 197.0–261.0) and the eyes of normal controls (211.8, 190.3–233.4).

Conclusions

HCF distributions correlated with the degree of fundus pigmentation in eyes with VKH disease. Quantitative measurements of HCF on en face OCT images can be a novel tool in evaluating choroidal pigmentation in patients with VKH disease.