Background: peribulbar block is commonly used for cataract surgery in adults, most commonly local anesthetics were injected into peribulbar space, but using only local anesthetics for peribulbar anesthesia is associated with delayed onset of globe akinesia and, short duration of analgesia and frequent need of block supplementation Objective: to assess the efficacy and safety of addition of dexmedetomidine versus magnesium sulphate to local anesthetic mixture for peribulbar block in cataract surgery. Patients and Methods: the patients were divided randomly into two equal groups: Dexmedetomidine group (D Group) included 30 patients who received 50 µg dexmedetomidine adjuvant to local anesthetics mixture (lidocaine and bupivacaine). Magnesium sulphate group (M Group) included 30 patients who received 50mg of Magnesium sulphate adjuvant to local anesthetics mixture (lidocaine and bupivacaine). Results: The addition of Dexmedetomidine or Magnesium sulphate to local anesthetic in cataract surgery accelerates the onset of corneal anesthesia and globe akinesia . The decrease in the IOP is more in D Group . No significant changes in the hemodynamic measurements in both groups Conclusion: Use of 50ug dexmedatomedine or 50mg magnesium sulphate 10% with mixture of lidocaine 2% plus bupivacine 0.5% for peribulbar anesthesia in cataract surgery enhances the onset of globe anesthesia and akinesia . Dexmedetomidine causes more decrease in intraocular pressure magnesium sulphate.