It is rare for isolated sphenoid sinusitis to cause orbital cellulitis. We present a rare case of posterior orbital cellulitis, so caused, together with a review of the relevant literature.

A 29-year-old woman presented with a 6-week history of progressive, unilateral, retro-orbital and periorbital right eye pain. On examination, the only finding was reduced visual acuity in the right eye. A computed tomography scan demonstrated right frontal and sphenoid sinus opacification. Sphenoidotomy and frontal sinus trephination were subsequently performed, following failure to respond to intravenous antibiotics. After surgery, the patient's vision returned to normal.

Isolated sphenoid sinusitis is rare but can cause significant visual disturbance and permanent loss of vision. Vague symptoms unsupported by clinical signs at presentation are a feature of posterior orbital cellulitis. The presented case highlights the problem, and the need for a high index of clinical suspicion even in the absence of firm clinical signs, in order to prevent permanent visual loss.