Introduction: Dysthyroid optic neuropathy (DON) is a rare, severe form of thyroid eye disease, in which decreased visual acuity is accompanied by characteristic MRI findings. The treatment of DON has always been a challenge.
Case presentation: In a patient in whom visual acuity deteriorated on the left eye, mannitol 20% 200 mL followed by furosemide 40 mg 6 h later, administered daily, were initiated on the day of admission. Visual function by ophthalmology methods, and orbital compartment volumes and water content by MRI were followed. Intravenous diuretics resulted in an immediate therapeutic response. Visual acuity improved from 20/50 to 20/25 after 2 days of treatment. MRI revealed decreasing water content of both the muscle and connective tissue compartments without any volume changes. Subsequently, corticosteroids and orbital irradiation were started. Orbital decompression surgery was not required.
Discussion/conclusion: Edematous swelling of orbital tissues is an established contributor of local pressure increase in thyroid eye disease. Diuretics reduce orbital pressure and, if confirmed by others, may be useful additions to the standard of care in sight-threatening DON.
Keywords: MRI; diuretics; dysthyroid optic neuropathy; thyroid eye disease.