Diplopia due to maxillary sinus mucocoele

Mucocoeles are cyst-like lesions of the paranasal sinuses, which may rarely erode through the bony orbit and so displace or compress orbital contents. Such patients may present to ophthalmologists and other health care professionals with diverse problems including facial pain and swelling, proptosis, double vision, ptosis, infra-orbital anaesthesia, epiphora and optic nerve dysfunction with reduced vision. We present an illustrated interventional case report of an 81-year-old gentleman with a 2-week history of swelling around the left lower eyelid and malar region associated with double vision both in the primary position and particularly downgaze. We discuss the aetiology, diagnosis and contemporary management of maxillary mucocoeles and also the Caldwell-Luc procedure. The article serves as a reminder that maxillary mucocoeles may slowly and covertly invade the orbit and should be considered in the differential diagnosis in patients presenting with proptosis, globe displacement and an orbital or adnexal mass.