Patients and methods: The investigators studied 2 groups of patients electively scheduled for laparoscopic cholecystectomy. The study group included 10 patients that were ventilated by high frequency jet ventilation (HFJV). In the control group (16 patients) the investigators used the standard intermittent positive pressure ventilation (IPPV). Both groups were matched according to clinical and hemodynamic parameters. Intra-ocular pressure was measured by a senior ophthalmologist that was blinded to the ventilation technique. Laparoscopic surgery was done as usual, and the intra-peritoneal pressure was automatically set on 14 mmHg. Statistical significance was considered whenever P value was less than 0.05.