Retinal Peripapillary Perfusion Changes in Thyroid-Related Orbitopathy with Asymmetric Proptosis without Compressive Optic Neuropathy Detected Using Optical Coherence Tomography Angiography

Abstract

Purpose : Thyroid-related orbitopathy (TRO) causes hemodynamic changes in the orbit from compression and congestion that may cause ischemic damage to the optic nerve. This study explores the retinal peripapillary perfusion in TRO eyes using optical coherence tomography angiography (OCTA).

Methods : We reviewed 4.5x4.5mm en face “RPC layer” OCTA scans of 6 TRO patients with asymmetric proptosis without compressive optic neuropathy and a clinical assessment score of less than 3 (12 eyes, mean age 41 years, range 23-69 years), and 133 healthy controls (133 eyes, mean 41.5 years, range 11-83 years). The 6 relatively less proptotic TRO eyes were grouped into Group A, while their relatively more proptotic fellow eyes (on average 1.67mm more proptotic) were grouped into Group B. A novel algorithm from our laboratory was used to automatically segment non-capillary from capillary peripapillary blood vessels and to calculate respective perfusion densities. ANOVA and pairwise Tukey-Kramer testing were performed to detect differences in perfusion densities between Groups A and B and the control group. Results are presented as average ± standard deviation. A p value of less than 0.05 was considered statistically significant.

Results : Noncapillary peripapillary perfusion density in TRO eyes was found to be significantly decreased compared to healthy controls (Group A 17.2±4.9% and Group B 13.6±3.4% vs. controls 21.5±4.7%; p=0.001). A greater decrease was noted in eyes with relatively more proptosis than in fellow eyes, however this difference did not reach statistical significance (Group A vs. Group B; p=0.12). Peripapillary capillary perfusion densities in all 3 groups (Group A 42.2±1.9% vs. Group B 42.2±2.0% vs. controls 42.5±1.5%) showed no significant difference. Clinical markers were not different between Groups A and B.

Conclusions : TRO eyes with more proptosis showed a greater decrease in noncapillary peripapillary perfusion, while capillary perfusion and routine clinical markers were not significantly affected. Intraorbital compression on the central retinal blood vessels in TRO may be responsible for these findings. OCTA provides a new sensitive tool for monitoring the subclinical hemodynamic effects on the optic nerve head in TRO, and may be useful for earlier diagnosis and assessment of treatment response.

This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.