Choroidal Thickness Associated with Thyroid-associated Ophthalmopathy Activity

Xianqun Fan, MD, PhD

Credit: Shanghai JiaTong University School of Medicine

A recent investigation evaluating the staging of thyroid-associated ophthalmopathy using swept-source optical coherence tomography (SS-OCT) revealed a significant association between subfoveal choroidal thickness (SFCT) and disease activity.¹

Thyroid-associated ophthalmopathy is an autoimmune inflammatory disease where orbital tissues undergo extensive remodeling - a challenging ocular component in patients with the autoimmune condition Graves’ disease.²

Results from this descriptive cross-sectional study showed SFCT, a marker of potential structural inflammation, was significantly thicker during the active disease stage than during inactive disease.¹ Given this accuracy in activity prediction, investigators suggest SFCT may provide a useful index during the evaluation of thyroid-associated ophthalmopathy.

“Notably, we found a significant association between SFCT and disease activity, where SFCT was significantly thicker during active disease than during inactive disease; this finding suggests that SFCT can serve as an auxiliary marker of disease activity,” wrote the investigative team, led by Xianqun Fan, MD, PhD, a professor in he department of ophthalmology at Shanghai Ninth People’s Hospital, Shanghai JiaTong University School of Medicine.¹

Accurate clinical assessment of the grade and severity of thyroid-associated ophthalmopathy is crucial to identify those likely to develop more severe complications and to provide appropriate management.² Treatment can depend on the assessment of disease activity and severity, with the current staging method based on the Clinical Activity Score (CAS), involving 7 clinical manifestations: spontaneous retrobulbar pain, eye rotation pain, eyelid edema, eyelid congestion, conjunctival edema, conjunctival congestion, and lacrimal caruncle swelling.³

However, as symptoms can fluctuate and exhibit differently across patients, the lack of objective and quantitative evaluation criteria can lead to subjective judgment in clinical practice.² Thus, there is a need for an objective evaluation method to improve early diagnosis.

Retinal thickness and choroidal thickness are potential markers of structural inflammation, making them useful for disease monitoring and prognosis prediction. SS-OCT can offer real-time acquisition of high-resolution, non-invasive cross-sectional subsurface tomographic images showing biological structures.

In this analysis, Fan and colleagues used SS-OCT to investigate choroidal thickness across various levels of thyroid-associated ophthalmopathy activity and severity.¹ Between December 2021 and May 2022, a total of 30 patients with thyroid-associated ophthalmopathy (60 eyes) and 38 sex-matched healthy controls (67 eyes) were recruited for the study.

The analysis used the CAS to grade disease activity; disease activity was assessed using standardized criteria proposed by the European Group on Grave’s Orbitopathy. Choroidal thickness was measured by SS-OCT.

Patients with thyroid-associated ophthalmopathy and healthy controls did not significantly differ in terms of axial length (P = .5865) or BCVA (P = .6187). The mean SFCT in patients with active disease was 276.23 ± 84.01 µm, while the thickness was 224.68 ± 111.61 µm in patients with inactive disease. Among healthy controls, the mean SFCT was 223.56 ± 78.69.

Analyses using Dunn’s test showed the mean choroidal thickness was significantly thicker in the active group than in the inactive group (P = .049) and additionally thicker in the active group than in the control group (P = .010). Investigators identified no differences in SFCT between patients with moderate-to-severe disease, those with severe disease, and healthy controls (P >.05).

Meanwhile, changes to SFCT showed strong prediction in distinguishing active thyroid-associated ophthalmopathy from inactive disease (area under the curve [AUC], 0.659; 95% CI, 0.496 to 0.822). Ganglion cell layer thickness, retinal nerve fiber layer thickness, and retinal thicknesses each showed weak predictive ability. Compared to these variables, ​​subfoveal thickness had a better diagnostic effect in distinguishing thyroid-associated ophthalmopathy from control (AUC, 0.605).

Multivariate analysis was performed with SFCT as the dependent factor and displayed positive associations with intraocular pressure (P <.001), best-corrected visual acuity (P = .005), and CAS (P = .019, but negative associations with axial length (P <.001).

“These results indicate that choroidal thickness decreases as axial length increases; conversely, choroidal thickness increases as CAS and IOP increase,” investigators wrote.¹

References

1. _{Zhong S, He F, Fang S, et alChoroidal thickness in patients with thyroid-associated ophthalmopathy, as determined by swept-source optical coherence tomographyBritish Journal of Ophthalmology Published Online First: 19 October 2023. doi: 10.1136/bjo-2023-323694}
2. _{Bartalena L, Piantanida E, Gallo D, et al. Epidemiology, natural history, risk factors, and prevention of graves' Orbitopathy. Front Endocrinol (Lausanne) 2020;11:615993. doi:10.3389/fendo.2020.615993}
3. _{Bartalena L, Kahaly GJ, Baldeschi L, et al. The 2021 European group on graves' Orbitopathy (EUGOGO) clinical practice guidelines for the medical management of graves' Orbitopathy. Eur J Endocrinol 2021;185:G43–67. doi:10.1530/EJE-21-0479}