RNFL thickness as measured by optical coherence tomography OCT has been shown to correlate very well with optic nerve atrophy and visual function in optic neuritis14, 15. Using OCT measurements of optic nerve and retinal nerve fiber layer (RNFL) thickness and visual field testing as the primary outcome, we hypothesize that high-dose aprotinin administration would decrease the incidence and severity of optic nerve and retinal injury following CABG with CPB.