BACKGROUND: Narcotics and sedatives can reduce intraocular pressure. This study was performed to evaluate the effect of remifentanil plus ketamine on intraocular pressure and sedation quality in comparison with fentanyl plus ketamine during and after operation in patients undergoing phacoemulsification with topical anesthesia. METHODS: Forty four patients were randomized into two groups to receive either a continuous infusion of remifentanil (0.2 μg/kg/min for 4 min and then 0.1 μg/kg/min: Group R, n=22) or bolus intravenous fentanyl (1.5 μg/kg: Group F, n=22) for sedation. Patients in both groups received low dose ketamine (0.15 mg/kg) intravenously. Topical anesthesia was performed using tetracaine 0.5% eye drop in both eyes. Intraocular pressure was measured in non-operative eye before sedation (baseline), 2 minutes after sedation, before intraocular lens insertion, at the end of operation and 15 minutes after the end of operation using Schi tz tonometer. Sedation, cooperation, satisfaction and pain scores and also postoperative nausea and vomiting were recorded in all patients. Surgeon satisfaction scores were evaluated at the end of operation. RESULTS: The intraocular pressure did not differ significantly between the two groups throughout the study. The mean (SD) intraocular pressures 2 minutes after sedation, before intraocular lens insertion, at the end of operation and 15 minutes after the end of operation in recovery room were all less than that of baseline in both groups, but the baseline value was decreased only significantly (P < 0.05) in recovery room [13.75 (3.46) to11.91 (3.43) in group R, respectively and 13.74 (3.05) to11.57 (2.33) in group F, respectively]. The incidence of postoperative nausea and vomiting in group R was higher than that of group F (7 patients in group R and no patient in group F, P = 0.009). CONCLUSIONS: Combination of remifentanil infusion and intravenous ketamine did not offer any advantages over the combination of intravenous fentanyl and ketamine in order to prevent intraocular pressure rising during phacoemulsification. The lower incidence of postoperative nausea and vomiting and higher rate of appropriate sedation in fentanyl group suggested fentanyl as a more suitable medication for systemic sedation compared with remifentanil. KEY WORDS: Fentanyl, remifentanil, intraocular pressure, phacoemulsification, topical anesthesia.