When patients with sinusitis do not improve after repeated courses of antibiotics and reasonable trials of other medications, the otolaryngologist, or ENT doctor, may recommend undergoing Functional Endoscopic Sinus Surgery, or FESS. Functional endoscopic sinus surgery is a minimally invasive technique used to restore sinus ventilation and normal function. The most suitable candidates for this procedure have recurrent acute or chronic infective sinusitis, and experience improvement in symptoms of up to 90 percent following the procedure. Fiber optic telescopes are used for diagnosis. During the procedure, a computed tomography is used to assess the anatomy and identify diseased areas.