Association Between Autonomic Symptoms and the Choroidal Vascularity Index in Fibromyalgia Patients

Background and Objectives: Fibromyalgia syndrome (FMS) is frequently accompanied by autonomic symptoms and autonomic dysregulation, which may influence ocular blood flow regulation. The choroid is a densely vascular, autonomically innervated tissue, and optical coherence tomography (OCT)-derived markers have been used to explore potential ocular microvascular changes in FMS, with inconsistent findings. The choroidal vascularity index (CVI), defined as the proportion of luminal area within the total choroidal area, has been proposed as a potentially more robust marker of choroidal vascular status than thickness alone. We aimed to compare CVI and choroidal thickness between patients with FMS and healthy controls and examine the association between autonomic symptom burden and CVI in FMS. Materials and Methods: This single-centre observational cross-sectional case-control study enrolled adults aged 18-65 years. Swept-source OCT was performed; low-quality scans were excluded, and only right eyes were analysed. CVI, subfoveal maximum and mean choroidal thickness were obtained using an artificial intelligence-assisted analysis platform. Autonomic symptom burden, fibromyalgia impact, and central sensitization-related symptoms were assessed using the Composite Autonomic Symptom Score-31 (COMPASS-31), the Revised Fibromyalgia Impact Questionnaire (FIQ-R), and the Central Sensitization Inventory (CSI), respectively. Group comparisons, Spearman correlations, and multivariable linear regression were performed. Results: COMPASS-31, FIQ-R, and CSI scores were higher in the FMS group (all p < 0.001). CVI and choroidal thickness did not differ significantly between groups (CVI p = 0.124; maximum thickness p = 0.136; mean thickness p = 0.097). CVI was not correlated with COMPASS-31, FIQ-R, or CSI within either group. In adjusted models, age was independently associated with CVI (p < 0.001), whereas FMS status and COMPASS-31 total score were not. Conclusions: CVI and choroidal thickness were similar in FMS and controls, and CVI was not associated with self-reported autonomic symptom burden in FMS. Studies incorporating objective autonomic testing and dynamic vascular imaging paradigms are warranted.