A Pilot Study of Subclinical Non-Capillary Peripapillary Perfusion Changes in Thyroid-Related Orbitopathy Detected Using Optical Coherence Tomography Angiography

Abstract

Purpose: Hemodynamic changes surrounding the optic nerve head are known to occur in thyroid-related orbitopathy (TRO). This pilot study explores the capillary and non-capillary peripapillary perfusion changes of the retina in TRO eyes without dysthyroid optic neuropathy (DON) using optical coherence tomography angiography (OCT-A).

Methods: Non-capillary and capillary peripapillary perfusion densities were calculated using single 4.5 × 4.5mm en face "RPC layer" OCT-A scans of 8 TRO patients without DON (8 eyes, mean age 40.6 years, range 23-69 years). Results were compared to a previously published dataset of 133 healthy controls (133 eyes, mean 41.5 years, range 11-83 years). The strength of association was measured between OCT-A perfusion densities and clinical measures of TRO.

Results: Non-capillary peripapillary perfusion density in TRO eyes was found to be significantly decreased compared to healthy controls (TRO group 15.4 ± 2.9% vs controls 21.5 ± 3.1%; p < 0.0001). Capillary peripapillary perfusion densities showed no significant difference (TRO group 42.5 ± 1.8% vs controls 42.5 ± 1.5%; p = 1.0). Clinical measures of disease did not correlate well with OCT-A perfusion densities (p>0.05).

Conclusion: These findings may represent decreased blood flow and subclinical ischemia to the optic nerve. We discuss possible pathogenic mechanisms of thyroid-related vasculopathy, including vessel wall thickening due to immunologically-induced media enlargement.

Keywords: optical coherence tomography angiography; peripapillary microvasculature; thyroid-related orbitopathy; thyroid-related vasculopathy.

Figure 1

(A) An original OCT-A 4.5×4.5mm “RPC layer” peripapillary scan. (B) A binary image of non-capillary blood vessels after global thresholding. (C) Original OCT-A image with the non-capillary vessel mask removed. (D) Segmented capillary blood vessels after local thresholding. (E) An original OCT-A “Choroid layer” peripapillary scan, with a 1.95-mm yellow circle demarcating the approximate optic nerve head margin. (F) The 0.75-mm-wide annular ROI, created by the 1.95-mm yellow circle and 3.45-mm concentric green circle. (G and H) Quantitative non-capillary and capillary peripapillary perfused density analysis was derived from the ROI. “T” denotes temporal, and “N” nasal, to the nerve.

Figure 2

Scatter plots of perfusion density (%) of TRO eyes compared to healthy control eyes. Black bars indicate group averages. (A) Non-capillary peripapillary perfusion density in TRO eyes was significantly decreased (asterisks; p < 0.0001). (B) Capillary peripapillary perfusion density in TRO eyes was not significantly different compared to that of healthy control eyes.

Figure 3

(A, C, E) Images of the right eye of Patient 5, compared to (B, D, F) that of the right eye of a 24-year-old male healthy control (age-, sex- and laterality-matched). (A and B) Optic nerve head color photos; and, (C and D) capillary and (E and F) non-capillary peripapillary perfusion density annuli, with respective density values indicated at the bottom of images. “T” denotes temporal, and “N” nasal, to the nerve.