Cognitive and neurological dysfunction after coronary artery bypass surgery (CABG) is common and multi-factorial in origin. Several previous studies have shown that intraoperative aprotinin administration may be neuroprotective.in the current prospective randomized study, the effect of intraoperative aprotinin administration on the integrity of the optic nerve and retinal nerve fiber layer will be examined. Optical coherance tomography will be used to examin the optic nerve and retinal nerve fiber layer.