The investigators measured changes in cerebral oxygen saturation (rSO2) and MMSE scores after retrobulbar block performed with levobupivacaine and lidocaine in patients undergoing vitreoretinal surgery.A total of 66 patients over the age of 60 undergoing vitreoretinal surgery with a total duration of less than 1 hour were included in this prospective, double-blinded study. The patients were randomly divided into two groups: group L (5ml, 2% lidocaine) and group LB (5ml, 0.5% levobupivacaine). Bilateral rSO2 measurements were recorded before the retrobulbar block and at 1-5 minutes post-block, during the procedure, and at 10-40 minutes post-op. MMSE was performed preoperatively and postoperatively in order to evaluate short term cognitive function. Sensory and motor block durations, pain, akinesia and conjunctival feeling scores, patient-surgeon satisfaction, and complications were also recorded.