Silent Sinus Syndrome is characterized by enophthalmos with onset in adulthood. It is caused by the collapse of some or all walls of the maxillary sinus. The prevalence is unknown; approximately 100 cases have been described in the literature to date. Progressive enophthalmos is sometimes accompanied by cheek pain, diplopia, and blurred vision. Patients sometimes recall having had sinusitis in the past. The syndrome is either idiopathic or occurs after bony decompression of the orbit for Graves' ophthalmopathy or after an orbital floor fracture.