Effect of Usage of Electroencephalogram (EEG) Entropy on the Incidence of Postoperative Cognitive Dysfunction in Geriatric Patients

Inclusion Criteria: * ASA physical status I-II. * scheduled for retinal surgery expected to take 2-3 hours under general anesthesia. * orotracheal intubation. Exclusion Criteria: * history of cardiac, pulmonary, liver or renal disease. * significant obesity (body mass index \>30. * Long-term user of central nervous system activator drugs, benzodiazepines and/or opiates. * dementia, brain atrophy and other neurological disorder.