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.In a patient in whom visual acuity deteriorated
on the left eye, mannitol 20% 200 ml followed by furosemide 40 mg 6 hours 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 immediate therapeutic response. Visual acuity improved from
20/50 to 20/25 after two 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.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.
