FESS or Functional Endoscopic Sinus surgery involves the insertion of the endoscope, a very thin fiber-optic tube, into the nose for a direct visual examination of the openings into the sinuses. With state of the art micro-telescopes and instruments, abnormal and obstructive tissues are then removed. In the majority of cases, the surgical procedure is performed entirely through the nostrils, leaving no external scars. There is little swelling and only mild discomfort.

The advantage of the procedure is that the surgery is less extensive, there is often less removal of normal tissues, and can frequently be performed on an outpatient basis. After the operation, the patient will sometimes have nasal packing. Ten days after the procedure, nasal irrigation may be recommended to prevent crusting