A Comparative Study of Oral Gabapentin, Oral Alprazolam and Intravenous Dexmedetomidine on Perioperative Anxiety and Pain During Posterior Segment Eye Surgery Under Peribulbar Block : a Randomized, Double-blind Study.

Inclusion Criteria: * Patients aged from 45 to 65 years old, of both sexes. * ASA 1-2. * Undergo posterior eye surgery (vitrectomy and retinal detachment) under peribulbar block. Exclusion Criteria:• Patient refusal. * Uncooperative patient. * Communication difficulty resulting from deafness or language barrier. * Chronic use of narcotics, barbiturate, psychotropic medications or claustrophobia. * Body weight less than 40 kg or more than 100 kg. * Known allergy to local anesthetics or any of the study drugs. * ASA 3-4. * Inability to lie supine for the time of surgery or involuntary movement. * Patients with baseline heart rate (HR) \<60/min, severe left ventricular dysfunction (EF \<30%), hypovolaemia with systolic blood pressure (SBP) \<90 mmHg, Mobitz type 2 or 3rd degree heart block, severe valvular disease (valve stenosis/regurgitation), asthma, chronic cough, upper respiratory tract infection within the previous 2 weeks, chronic renal failure and hepatic impairment will be excluded from the study. * Patients on medications can affect the removal of alprazolam from the body, which may affect how alprazolam works. Examples include azole antifungals (such as itraconazole, ketoconazole),cimetidine, certain antidepressants (such as fluoxetine, fluvoxamine, nefazodone ),drugs to treat HIV( delavirdine, protease inhibitors such as indinavir), macrolide antibiotics (such as erythromycin), rifamycins (such as rifabutin), St.John's Wort and drugs used to treat seizures (such a…