Too much of a good thing

A 38-year-old man with poorly controlled type 2 diabetes mellitus and arterial hypertension on semaglutide presented with acute, painless, vision loss in the left eye. Ophthalmic examination revealed optic disc edema (ODE) in the left eye and optic disc pallor (ODP) in the right eye, accompanied by severe nonproliferative diabetic retinopathy and cystoid macular edema in both eyes. The combination of ODE in one eye and ODP in the fellow eye raised concern for the Foster Kennedy syndrome secondary to an intracranial mass; however, neuroimaging and systemic evaluation were unremarkable. Ultimately, it was decided the ODP was due to a prior unrecognized non-arteritic anterior ischemic optic neuropathy (NAION) event, and the ODE was the result of an acute NAION in the symptomatic fellow eye (i.e. pseudo-Foster Kennedy syndrome).