Assessment of choroidal perfusion indices in thyroid eye disease by using optical coherence tomography.

Purpose: To study choroidal vascularity changes in active and inactive TED orbits by using high-definition optical coherence tomography (HD-OCT) and correlate the changes with the duration and severity of TED and Barrets' index.

Methods: A cross-sectional study wherein 37 TED orbits and 30 healthy control (HC) orbits were enrolled. Choroid was imaged using HD-OCT scans centered at the fovea, and subfoveal choroidal thickness (SFCT) was measured. The OCT images were analyzed using ImageJ software to calculate choroidal vascularity index (CVI) and associated choroidal perfusion indices.

Results: The study included eight active, 13 non-inflammatory active (NIA), and 16 inactive TED orbits. The mean age was 39.73 ± 12.91 years, and the male: female ratio was 1.18:1. Intraocular pressure and CVI were higher, while SFCT was similar in TED on comparison to healthy orbits. CVI and SFCT were raised in active as compared to inactive TED. CVI and SFCT correlated positively with Barrets' index and negatively with the duration of thyroid disease. The area under curve of CVI (95% CI: 0.651-0.864, P < 0.001) helped in differentiating TED orbits from HC, while CVI (95% CI: 0.780-0.983, P < 0.001) had the maximum discriminatory power in predicting the activity of disease.

Conclusions: CVI has greater sensitivity than SFCT in differentiating healthy from TED orbits. The blood flow stagnation in active orbits, which improves during the course of TED and tends to worsen with increase in Barret's index, can lead to choroidal vascularity changes. CVI and SFCT can act as adjunct to existing modalities for monitoring the disease activity.