PURPOSE: To evaluate choroidal and optic disc alterations in eyes with thyroid eye disease (TED) compared with healthy eyes by using TowardPi widefield optical coherence tomography angiography (OCTA). METHODS: This was a retrospective cross-sectional cohort study. A total of 112 participants (60 TED patients and 52 healthy controls) underwent TowardPi widefield OCTA, which provided detailed demographic and clinical data. Three-dimensional choroidal data, including thickness, vascular metrics, and optic disc measurements, were obtained from the built-in software. RESULTS: The study included 24 eyes with dysthyroid optic neuropathy (DON), 24 eyes with active non-DON TED, 71 eyes with inactive TED, and 104 healthy eyes. Choroidal thickness significantly decreased in the optic disc region during the DON phase (148.71 ± 78.98 µm) compared to normal eyes (182.35 ± 51.98 µm) and inactive TED eyes (191.34 ± 58.86 µm) (P = 0.030). In DON, choroidal stromal volume was reduced (34,183.81 ± 10,649.01 × 106 µm3) compared to normal (46,339.53 ± 16,711.99 × 106 µm3) (P = 0.002), whereas the choroidal vascular index increased (42.67% ± 3.41%) compared to normal (38.53% ± 6.35%) (P = 0.002). Optic disc area increased in DON (1.99 ± 1.24 mm2) compared to inactive TED (1.39 ± 0.38 mm2) (P <
0.001), along with reduced retinal nerve fiber layer blood-flow density in DON (45.09% ± 3.07%,) compared to normal (47.84% ± 1.41%) (P <
0.001). CONCLUSIONS: This study highlights the critical role of choroidal and optic disc alterations in TED pathophysiology and underscore the utility of widefield OCTA in identifying these changes, particularly in DON-risk patients.