 Serious complications such as blindness occur in only 0.44% of cases, as determined by a study performed in the United Kingdom.A Cochrane review in 2006 based on three randomized control trials concluded that FESS has not been shown to provide significantly better results than medical treatment for chronic rhinosinusitis.Another Cochrane review looked at postoperative care of patients after FESS using debridement (removal of blood clots, crusts, and secretions from the nasal and sinus cavities under local anaesthetic), but the evidence from the available clinical trials was uncertain.