Lateral Flare Sign of Thyroid-Associated Eye Disease

A 44-year-old male smoker presented with a six-month history of bulging and redness in his right eye. He also reported intermittent binocular double vision, which was more noticeable on upward gaze. There was no history of trauma, headache, vision loss, or tachycardia. Systemic examination was unremarkable. On examination, the patient had conjunctival redness, hyperemia, proptosis, and swelling with temporal flaring of the right upper eyelid (Figure 1A). Ocular motility and visual acuity were within normal limits. Thyroid function tests revealed TSH: 0.81 (reference range: 0.35–5.50), Free T4: 1.7 (0.80–2.19), and T3: 1.58 (0.87–1.78). Orbital MRI showed right eye proptosis and significant thickening with edema of the right inferior rectus muscle, without involvement of other extraocular muscles (Figure 1B). The TSH receptor antibody (TRAb) level was elevated at 2.38 IU/L (reference: <1.22).