Intraocular Pressure in Lumbar Spine Fusion Patients – A Randomized , Prospective Study

Introduction: Ischemic optic neuropathy (ION) resulting in visual loss is a rare but devastating complication in spine surgery. Procedure time, blood loss, prone position and systemic factors may contribute to the risk of perioperative blindness. Elevated intraocular pressure (IOP) results in decreased perfusion and possibly ION. We evaluated the effect of head positioning on IOP in lumbar spine fusion patients. Methods: Surgeries were performed on 52 patients at one institution. Inclusion criteria were lumbar spine fusion in patients 18-80 years old. Exclusion criteria included eye disease or injury, history of cervical stenosis, neck pain, trauma or current neoplasm. The control group had the head in neutral position with the face parallel to the level operating room table and the experimental group had the neck extended so the face had an angle of inclination of 10° with the table. All patients were managed with Gardner-Wells tongs and ten pounds of traction on a Jackson table. Using an applanation tonometer, one author made all IOP measurements in pre-operative holding, supine after anesthetic induction, prone after positioning on the table and at regular intervals throughout the case. IOP measurements were recorded with respective time points and corresponding blood pressure and CO2 values. Independent variables included age, duration of procedure, blood loss, type/amount of fluid replacement, blood pressure, PCO2, gender and head position. Results: Data were analyzed using ANOVA for categorical risk factors and with regression analysis for continuous risk factors. Mean values for IOP measurements in the prone position were statistically significantly lower in the 10° elevated group versus the head-neutral group (p=0.0014). No patient sustained visual loss or any cervical spine related complications. Conclusion: Ten degree elevation of the head in the prone position for adult lumbar spine fusion patients resulted in statistically significantly lower IOP measurements compared to controls. As lower IOP correlates with increased optic nerve perfusion, this positioning intervention could mitigate the risk of perioperative blindness in spine surgery patients in the prone position.