Cognitive Dysfunction After Cataract Surgery

* Cataract surgery is commonly performed in elderly patients who are at high risk for developing postoperative cognitive dysfunction. Most cataract surgeries are performed under peribulbar or retrobulbar anesthesia, however, most of the patients require sedation to relieve the perioperative anxiety and induce amnesia. So, many sedative agents can be used especially benzodiazepines which may increase the risk of developing postoperative cognitive dysfunction. * Ketamine can be used as a sedative and analgesic agent in a dose of 0.25 -0.5 mg/kg with certain studies suggesting that it may decrease the risk of postoperative cognitive dysfunction. Similarly, dexmedetomidine can be used as a sedative and analgesic agent with the possibility of decreasing the incidence of postoperative cognitive dysfunction. * this controlled study will compare the effect of ketamine or dexmedetomidine on the POCD of patients undergoing cataract surgery.