An observational comparative study to evaluate the ocular changes in patients undergoing spine surgery in prone position under Total Intravenous Anaesthesia versus Balanced Anaesthesia

We propose to conduct a observational comparative study of the ocular pressure changes- intraocular pressure(IOP),mean arterial pressure( MAP) ,ocular perfusion pressure(OPP)  in patients undergoing spine surgery in prone position when maintained intraoperatively under Total intravenous anaesthesia versus  Balanced Anaesthesia. Prone  position is used for posterior approach in spine surgery, such positioning is known to cause ocular changes due to pressure on the orbital content and the altered hemodynamics(MAP) leading to increase intraocular blood volume thus IOP and OPP; hypoxia to optic nerve, ischemic optic neuropathy ,visual loss are some of the ocular changes observed. Thus the study is done in comparison to establish a protocol to prevent and anticipate the ocular changes. Patients will undergo pre anaesthetic checkup prior to surgery. Informed consent will be obtained from patients who meet the inclusion criteria. We will measure IOP, MAP, HR before induction, 5 min after induction and at the end in supine position, 5 min after extubation then OPP will be calculated from IOP and MAP, post-operative outcome and any adverse events during the surgery will be recorded.