The impact of graves' orbitopathy on anterior segment structures and choroidal parameters

To evaluate Schlemm's canal (SC) dimensions and choroidal vascularity in patients with Graves' orbitopathy (GO+), and to compare the findings with those of patients with Graves' disease (GD) without orbitopathy (GO-) and healthy controls using optical coherence tomography (OCT); additionally, to investigate the potential impact of these anatomical and vascular changes on intraocular pressure (IOP) elevation and glaucoma susceptibility.

This cross-sectional study included 164 participants, categorized into three groups: GO+ (n = 38), GO- (n = 76), and healthy controls (n = 50). All subjects were euthyroid for at least six months. SC length (SCL), SC area (SCA), choroidal vascularity index (CVI), luminal area (LA), stromal area (SA), and total choroidal area (TCA) were assessed. Correlations between SCA, SCL, and CVI measurements and other ocular and systemic parameters were analyzed. Demographic, ocular, and systemic parameters were also compared among groups.

There were no significant differences in age, sex, intraocular pressure, central corneal thickness, retinal nerve fiber layer thickness, or optic disc parameters across groups (p > 0.05). Hertel exophthalmometry values were significantly elevated in the GO + group (p < 0.001). Both SCL and SCA were significantly lower in the GO + group compared to the GO- and control groups (p < 0.001). The GO- group showed significantly reduced SC measurements compared to controls (p < 0.001). While CVI did not differ significantly among groups (p = 0.758), pairwise analysis revealed significantly higher LA (p = 0.028) and TCA (p = 0.035) levels in the GO + group compared to the GO- group. A borderline correlation was observed between SCA and CVI (r = 0.150, p = 0.050), and a significant negative correlation was noted between Hertel values and SCA (r = - 0.394, p < 0.001).

Changes in SC and choroidal structures in GD may be influenced by both mechanical and systemic factors. While these alterations may contribute to IOP elevation, they do not directly imply increased glaucoma risk but could play a role in its development or progression in susceptible individuals.