Neuro-ocular Effects of Spaceflight

Abstract

During long-duration spaceflight, approximately half of the astronauts develop a unique set of structural and functional neuro-ophthalmic changes to varying degrees including swelling of the optic disc, posterior ocular globe flattening, and hyperopic refractive error shifts. While the etiology of these changes remains unknown, hypothesized contributing factors include headward fluid shifting due to reduced gravity, cerebral venous congestion, increased intracranial pressure relative to the upright posture on Earth, and exposure to elevated carbon dioxide levels. Research efforts have turned to the development of spaceflight-compatible countermeasures to combat this spaceflight-associated neuro-ocular syndrome (SANS). Promising countermeasures include lower body negative pressure, thigh cuffs, and artificial gravity via human centrifugation, all aimed at redistributing body fluids to the lower limbs, similar to the upright position on Earth. Overall, effective countermeasures to the neuro-ophthalmic changes associated with extended exposure to the spaceflight environment, whether mechanical or pharmaceutical, must be developed to ensure both safe and successful deep space and exploration class missions in the future.