Orbital apex syndrome represents a heterogeneous group of disorders. It involves damage to the third, fourth and sixth nerves and the ophthalmic division of the fifth cranial nerve, and results in optic neuropathy. An 80‐year‐old man presented to our emergency clinic with left acute visual loss and three‐day history of ocular pain. His medical and ophthalmic history involved diagnosis of lung cancer and chalazion excision two weeks prior to presentation. There was total left ophthalmoplegia, vision was ‘no light perception’ and he had a relative afferent pupillary defect. An urgent computed tomography scan of the orbits showed sub‐periosteal abscess on the lateral wall of the orbit extending to the optic canal. The muscle cone was unaffected. The diagnosis was orbital apex syndrome. He underwent urgent drainage of the abscess and Staphylococcus aureus was identified with Gram stain. He was systemically administered intravenous antibiotics and steroids. His visual acuity and ophthalmoplegia improved rapidly 12 hours after surgery. Prompt diagnosis and treatment in cases of orbital apex syndrome, especially in immunocompromised patients, is important to prevent visual and life‐threatening complications.