Acute dysthyroid optic neuropathy exacerbated by orbital radiotherapy.

A 76-year-old lady presenting with acute dysthyroid optic neuropathy (DON) was stabilised with systemic intravenous methylprednisolone (IVMP). Two separate attempts at a treatment course of orbital radiotherapy (OR) were commenced and subsequently abandoned as there was an acute worsening of her DON during OR, despite cover with oral glucocorticoids and subsequently IVMP. The patient underwent urgent orbital decompression which normalised her vision and optic neuropathy. Our case likely represents worsening of DON due to soft tissue swelling secondary to OR despite cover with IVMP in a patient previously responsive to IVMP alone. Some authors advocate the use of OR in active DON as either a surgery delaying or surgery sparing alternative. This case report illustrates the rare risk of transiently worsening DON with OR. We highlight the need for close monitoring of optic nerve function if OR is utilised in this patient group.