Optic neuropathy in 2 thyroidectomized patients with moderate to severe Graves’ ophthalmopathy following L-thyroxine withdrawal prior to radioiodine treatment for thyroid carcinoma

Objective: To report on 2 patients with moderate to severe Graves ophthalmopathy (GO) who developed dysthyroid optic neuropathy following levothyroxine (LT4) withdrawal in preparation for 131I treatment for thyroid carcinoma. Methods: Two patients referred to a center for the treatment of thyroid diseases were evaluated. Results: Patient 1, a 55-year-old woman, had active (clinical activity score [CAS], 5 out of 7] moderate to severe GO. After LT4 withdrawal, her left eye visual acuity decreased from 10/10 to 1/10, and her omolateral visual field was impaired. Euthyroidism was rapidly restored and GO was treated with intravenous glucocorticoids. Nevertheless, as the patient’s visual acuity was still impaired, orbital decompression was performed. Patient 2, a 50-year-old man, had active (CAS, 3 out of 7) moderate to severe GO. After LT4 withdrawal, the patient developed a right dysthyroid optic neuropathy. His visual acuity decreased from 10/10 to 4/10, and his omolateral visual field was impaired. After prompt restoration of euthyroidism and treatment with intravenous glucocorticoids, normalization of his visual acuity was achieved.