On the day of surgery patients will be shifted into the operation theatre large bore I.V line access will be secured and Standard ASA monitors will be attached with non-invasive blood pressure (NIBP), electrocardiogram (ECG), heart rate, pulse oximetry. Hemodynamic parameters will be recorded. Baseline values of Optic nerve sheath diameter will be recorded by ultrasonography (by an experienced radiologist) and intraocular pressure will be recorded in supine position using Perkins applanation tonometer (by an experienced ophthalmologist) before general anaesthesia.  Anaesthesia protocol was standardized for drugs used in this procedure, after baseline measurement and adequate preoxygenation with 100% O2 for 3 min, Inj Glycopyrrolate 0.005mg/kg I.V and Inj midazolam 2mg I.V and Inj Fentanyl (2-3mcg/kg) I.V will be administered. Induction with Inj Etomidate 0.2mg-0.3mg/kg I.V , after loss of consciousness patient will be started with Inj Dexmedetomidine 0.5µg/kg loading dose followed by administration of 0.4 µg/kg/hr (in dexmedetomidine group)/ Inj Mannitol 0.5g/kg(in mannitol group) (these two drugs are prepared and kept concealed). Following patient will be given muscle relaxation using Inj atracurium (0.4-0.5mg/kg) I.V and after adequate ventilation for 3 mins Endotracheal  intubation will be performed by an anaesthesiologist and patient will be ventilated in volume control mode with Isoflurane as inhalational agent. During laparoscopic surgery intraperitoneal insufflation of CO2 will be  maintained  around 15mm Hg, IOP & ONSD will be measured 5mins after insufflation CO2 then patient position will be changed into trendelenburg position(>20 degrees from horizontal- measured with IV stand ), IOP and ONSD will be measured 10mins after the patient position changed in TP and measurement of IOP & ONSD will be measured at a time interval of 30mins & 60mins after making the patient in Trendelenburg position, CO2 insufflation will be stopped and evacuated by manual compressions of abdomen by open trocars, patient position will be returned to supine position, IOP and ONSD will be measured before extubation, after discontinuing volatile anaesthetics and patients will be given reversal dose of  Inj Neostigmine 0.05mg-0.08mg/kg, after adequate suction and subsequent attempts of respiration patient will be extubated and patients will be taken up to post-operative ward.