Antitumour necrosis factor alpha agents are important treatments in many inflammatory conditions including rheumatoid arthritis, psoriatic arthritis and the inflammatory bowel diseases. However, there have been case reports of optic neuritis and other demyelinating diseases as complications of these agents. This case report presents a patient with ulcerative colitis on infliximab who presented with sudden onset mono-ocular visual field loss and highlights the diagnosis and management of infliximab-induced optic neuritis.