APPROXIMATELY 29% OF ASTRONAUTS ON SHORT-TERM (~2 WK) SPACE SHUTTLE FLIGHTS AND 60% ON LONG-DURATION (~6 MO) MISSIONS TO THE INTERNATIONAL SPACE STATION (ISS) ARE REPORTED TO HAVE EXPERIENCED SOME IMPAIRMENT IN DISTANT OR NEAR VISUAL ACUITY. THESE VISUAL DISTURBANCES HAVE BEEN HYPOTHESIZED TO BE RELATED TO INCREASES IN INTRACRANIAL PRESSURE (ICP) AND INTRAOCULAR PRESSURE. MODELING STUDIES HAVE SHOWN THAT A COMPROMISE IN THE INTEGRITY OF THE VASCULAR BLOOD-BRAIN BARRIER (BBB) WOULD SERVE TO ELEVATE ICP. WHILE MUCH ATTENTION HAS BEEN DIRECTED TOWARD THE ROLE OF THE CEREBRAL VASCULATURE IN ELEVATING ICP LITTLE WORK HAS BEEN DONE TO EXAMINE CONDITIONS OF THE VASCULATURE IN THE EYE AND THE POTENTIAL ROLE OF MICROGRAVITY IN ALTERING THE BLOOD-RETINAL BARRIER (BRB) WHICH MAINTAINS A SIMILAR FUNCTION IN THE EYE FOR REGULATING INTRAOCULAR PRESSURE AS THE BBB IN THE CRANIUM. ONE CONDITION KNOWN TO COMPROMISE THE BRB IS OXIDATIVE STRESS. FOR EXAMPLE IN DIABETIC RETINOPATHY THE LEADING CAUSE OF BLINDNESS IN WESTERN SOCIETY ELEVATIONS IN OXIDATIVE STRESS COMPROMISE THE BRB AND INCREASE VASCULAR PERMEABILITY IN THE EYE. THE PROPOSED STUDIES THROUGH THE ISS RODENT TISSUE SHARING OPPORTUNITY WILL PROVIDE NEW AND IMPORTANT INFORMATION REGARDING THE EFFECTS OF SPACEFLIGHT ON OXIDATIVE STRESS IN THE EYE AND ITS POTENTIAL DELETERIOUS EFFECTS ON THE BRB.