Clinical Reasoning: A 79-Year-Old Woman With Subacute Bilateral Visual Loss

A 79-year-old woman presented with a 10-day history of rapidly progressive bilateral visual loss with more prominent involvement of the right eye. Her medical history was significant for an infiltrative breast carcinoma treated with mastectomy and chemotherapy (cyclophosphamide, doxorubicin, and paclitaxel) 1 year before, complicated by bilateral foot paresthesias and decreased sensation. The patient achieved complete remission from cancer and maintained regular oncologic follow-up. On admission, vision was limited to hand motion in the right eye and markedly reduced in the left eye (20/50), so that she was unable to read. Color vision was untestable in the right eye and remained intact in the left eye. A right relative afferent pupillary defect (RAPD) was observed. Intraocular pressure was normal, whereas funduscopic evaluation revealed bilateral optic disc swelling. Extraocular movements were full and not painful and other cranial nerves were intact. The rest of the neurologic examination was unrevealing, apart from signs of a distal symmetric sensory polyneuropathy.