Functional Endoscopic Sinus Surgery (FESS) is a surgery done mainly done for a chronic sinus disease like sinonasal polyposis, allergic fungal sinusitis,etc. The surgery make use of an endoscope and no external incision is made. The Endoscopic Surgery can also be applied to repair a CSF leak, removal nasal and sinonasal tumours, orbital surgeries, pituitary surgeries, infections of the lacrimal sac,etc.