OCT-A Identifies Increased Choroidal Thickness, Reduced Vessel Density in TAO Patients

The image above from the study shows representative maps of (A) choroidal thickness, (B) choriocapillaris density, (C) large-vessel choroidal layer thickness and (D) large-vessel choroidal layer density in a TAO eye. The study’s findings highlight a strong association between choroidal remodeling, specifically the thickening of the large-vessel choroidal layer and the progression of TAO. The study emphasizes that choroidal changes in TAO are part of a multifactorial process involving mechanical compression, inflammatory-mediated stromal remodeling and impaired vascular dynamics. Photo: Liu G, et al. Ophthalmol Sci. May 7, 2026. Click image to enlarge. Recent advances in ultra-widefield swept-source OCT angiography (OCT-A) have introduced a high-resolution imaging method for evaluating choroidal vascular alterations in diabetic retinopathy and retinal vein occlusion patients; however, data on using it on thyroid-associated ophthalmopathy (TAO) patients remains limited. In a recent study, researchers analyzed choroidal structural thickness and blood flow in these patients and found choroidal thickening was most pronounced in the central and nasal regions. The findings were reported in Ophthalmology Science.The study included 65 eyes from 35 TAO patients (mean age 51.8), comprising five mild, 40 moderate-to-severe and 20 dysthyroid optic neuropathy (DON) eyes. A control group of 70 eyes from 38 age- and sex-matched healthy subjects was also included. Swept-source OCT-A imaging was performed to capture datasets divided into nine subfields. Automated segmentation was used to measure structural thickness (whole choroid, large-vessel choroidal layer) and vascular density (choriocapillaris, large-vessel choroidal layer). Parameters were compared between TAO and control eyes, and subgroup analyses were conducted between DON and non-DON eyes.TAO eyes exhibited significantly greater mean whole choroidal thickness (189.9µm vs. 182.4µm) and large-vessel choroidal layer thickness (161.4µm vs. 149.9µm). Notably, the researchers observed significant choroidal thickening in the superior, inferior and nasal regions, which aligns with previous findings. These localized changes may be linked to extraocular muscle involvement, as muscle thickening predominantly affects the inferior and medial rectus muscles, followed by the superior and lateral rectus muscles, they added.TAO eyes showed reduced vascular density in the large-vessel choroidal layer (39.9% vs. 40.5%). Choriocapillary density showed a non-significant decrease.These results suggest that the choroidal stromal edema is the primary driver of choroidal thickening rather than vascular engorgement. Supporting this, we detected increased average large-vessel choroidal layer thickness in TAO eyes, particularly in the central, inferior and nasal regions. Notably, these changes in the large-vessel layer align with the observed overall choroidal thickening.“The combination of increased structural thickness and reduced vascular density suggests that choroidal thickening in TAO is driven primarily by non-vascular stromal edema rather than vascular engorgement,” the authors wrote in their paper.Subgroup analysis showed significant differences were primarily observed in eyes with DON, as they displayed significantly greater choroidal thickness compared to both non-DON TAO eyes and healthy controls. Non-DON TAO eyes showed no significant thickness changes relative to controls.The authors concluded that the discrepancy of increased choroidal thickness and decreased blood flow may be explained by several underlying processes: (1) extracellular matrix remodeling and stromal edema contributing to choroidal expansion independent of vascular dilations; (2) vascular compression resulting from elevated orbital pressure and stromal edema, which might lead to reduced luminal flow, despite compromised arterial supply and impaired venous drainage; and (3) altered autoregulatory mechanisms in orbital vessels may disrupt the typical relationship between vascular morphology and perfusion. However, they added, the precise regulation of choroidal blood flow in TAO remains under explored.Click here for the source. Liu G, Jiang K, Wang M, et al. Quantitative analysis of choroidal thickness and blood flow in thyroid associated ophthalmopathy using ultra-wide field swept-source OCT angiography. Ophthalmol Sci. May 7, 2026. [Epub ahead of print.]  This article was developed by the editorial staff in conjunction with experts in the field. In the process, AI may have been among the editorial tools used to meet the goals of human editors, who approved all content.