Functional Enoscopic Sinus Surgery (FESS) is a surgical modality for some diseases of the nose and paranasal sinuses. It is a relatively recent surgical procedure that uses the help of nasal endoscopes (which make use of Hopkins rod lens telescopes): these are endoscopes which have diameters of 4mm and 2.7mm and come in varying angles of vision from 0 degrees to 30, 45, 70, 90, and 120 degrees. These provide good illumination and can be introduced into the nose after anesthetising.