 Spine surgery in the prone position which involves lying face down is associated with various visual changes, ranging from temporary changes in acuity or sharpness to permanent blindness. Known risk factors include low blood count anemia and long surgical times in the prone position under general anesthesia. While blindness is a rare outcome of this surgery, it is devastating and incompletely prevented by controlling known risk factors. Thus, improved monitoring and detection of visual injury during surgery is necessary. The purpose of this study is to determine whether a novel, non-invasive monitoring device can reliably record visual responses during spine surgery. The first phase of this study is completed and involved patients undergoing microdiscectomy surgery. The second phase of this study involves patients undergoing single-level lumbar spine decompressionfusion surgery. 