Topical anaesthesia of the eye for ophthalmologic procedures avoids pain and discomfort of local anaesthetic injection in the peribulbar or retrobulbar block so that patient comfortability is achieved. Sedation during topical anaesthesia of the eye is mostly required to achieve anxiolysis, amnesia and keeping the patient calm all through the procedure. In the present study, the investigators will investigate the effect of nalbuphine/dexmedetomidine versus nalbuphine/propofol on the sedation as a primary outcome, intra-operative, postoperative analgesia, vital signs, patient and surgeon satisfaction and side effects as secondary outcomes

In both groups, the patients will receive i.v. nalbuphine 50 μg/kg. Patients in group D, will receive an i.v. loading dose of dexmedetomidine 1 μg/kg over 10 min followed by a maintenance infusion of 0.5 μg/kg/h. Patients in group P, will receive a bolus i.v. dose of propofol 0.5 mg/kg followed by an infusion started at 0.025 mg/kg/min .If sedation score was <3, rescue sedation with boluses of midazolam 0.01 mg/kg will be given. If the patient complained of pain (Numerical verbal pain rating scale ≥3) during the surgery, i.v. fentanyl 50 μg will be given as an intra-operative rescue analgesic and the surgeon will be instructed to use additional topical local anaesthetic eye drops if appropriate. After the completion of surgery, all infusions will be stopped, and the patients will be shifted to the postanaesthetic care unit (PACU) to be monitored for 2 hours before discharge.

Inclusion Criteria:

• Both genders,
• 20 and 65 years,
• American Society of Anesthesiologists (ASA) physical status I and II,
• Scheduled for cataract extraction surgery under topical anaesthesia.

Exclusion Criteria:

• Known allergy to local anaesthetics,
• Allergy to study drugs,
• Second or third-degree heart block,
• Alcohol or drug abuse
• Morbid obesity, pregnant and lactating females,
• Patients with severe cardiac, renal and hepatic disorders.

An independent anaesthesiologist not involved in the study will open the randomisation envelope just before the premedication and will prepare the appropriate drug-filled syringes according to the code and will not take part in the management and observations. (Syringes and infusion lines will be concealed by wrapping with an aluminium foil). A blinded investigator that will not be involved in the anaesthetic management of the patients, will collect the intra-operative and postoperative data.