Choroidal Structural Alterations in Patients with Subclinical Hypothyroidism: Cross-Sectional Study

Objective: Subfoveal choroidal thickness (SFCT) and variables of the stromal and luminal components of the choroid were investigated in patients with subclinical hypothyroidism (SCH), to gain insights into the pathology of choroidal alterations in this condition. Material and Methods: In this cross-sectional, observational study, one eye of each of 34 patients with SCH and of 34 control individuals were included. Choroidal structure was examined by enhanced-depth imaging optical coherence tomography. Choroidal measurements, particularly Choroidal Vascularity Index (CVI), Choroidal Stromal Index (CSI), and choroid-stromal-to-luminal-area ratio (C-SLR), were compared between the groups. Results: The SFCT and CVI were significantly higher in patients with SCH than in controls (p=0.014, p=0.009, respectively). Although the mean total choroidal area and luminal area was significantly greater in patients with SCH than in controls (p=0.038, p=0.012, respectively), the CSI, stromal area, and C-SLR did not differ significantly between the groups (p>0.05). The SFCT and CVI were significantly lower in patients with SCH who were older and had longer axial length, after adjusting for potential confounders (p<0.05). Conclusion: The choroid becomes thicker in SCH and is accompanied by an increase in the CVI. The significant increase in the luminal area suggests that choroidal thickening might arise from microvascular changes. Older age and longer axial length were associated with lower SFCT and CVI values.