Functional endoscopic sinus surgery (FESS) is a minimally invasive surgical treatment which uses nasal endoscopes to enlarge the nasal drainage pathways of the paranasal sinuses to improve sinus ventilation. This procedure is generally used to treat inflammatory and infectious sinus diseases, including chronic rhinosinusitis that doesn't respond to drugs, nasal polyps, some cancers, and decompression of eye sockets/optic nerve in Graves ophthalmopathy. In the surgery, an otolaryngologist removes the uncinate process of the ethmoid bone, while visualizing the nasal passage using a fiberoptic endoscope. FESS can be performed under local anesthesia as an outpatient procedure. Generally patients experience only minimal discomfort during and after surgery. The procedure can take from 2 to 4 hours to complete