“…Orbital apex syndrome (OAS) is a syndrome due to lesions in the orbital apex region, which is associated with dysfunction of cranial nerves II, III, IV, VI and the ophthalmic branch of the trigeminal nerve (V1) with optic nerve dysfunction [1,2]. OAS has many etiologies, infection is less commonly reported, if happened, the progression is rapid, and the prognosis is extremely poor [3]. Among the few cases of infection, the pathogens are fungi and aerobic bacteria [4], while anaerobic bacteria are rarely reported, especially the newly discovered species of anaerobic bacteria, Peptostreptococcus stomatis.…”