Intraocular Pressure During Prone Spinal Surgery

Study Summary

Postoperative visual loss resulting from surgical procedures not performed on the eye is a devastating outcome for the patient and poorly understood by the medical community. It is potentially a preventable complication. Diminished blood supply to the optic nerve, affecting both the anterior or posterior portions of the optic nerve, is the most common cause of postoperative visual loss. Other, less common causes include occlusion of the retinal artery and vein, a retinal embolism and cortical blindness. The incidence of postoperative visual loss increases in patients undergoing cardiopulmonary bypass and prone spinal surgery. Although the etiology of postoperative visual loss is unknown, it is thought to be multifactorial, and several potential risk factors have been identified, including degree of low blood pressure, preoperative hematocrit, external compression of the eye, amount of blood loss, prolonged duration of surgical time and lying in the face down position. The investigators believe this study is a unique opportunity to examine the mechanisms responsible for the antecedents to postoperative visual loss (POVL) and ischemic optic neuropathy (ION), a devastating complication of (usually) an elective surgical procedure. The purpose of this research is to try and determine the potential variables responsible for postoperative visual loss which will assist the medical community in devising methods for its prevention.

Interventions

• OTHER table tilt