Spaceflight-Associated Neuro-ocular Syndrome (SANS): a review of proposed mechanisms and analogs

Introduction: Over the last decade, many neuro-ocular findings have been documented following long-duration spaceflight (LDSF) including optic disc edema, choroidal folds, hyperopic refractive shift, and cotton wool spots. These are currently classified under the term Spaceflight-Associated Neuro-Ocular Syndrome (SANS). SANS is unique to space flight with no direct terrestrial analog. The exact pathogenesis is a subject of much debate and poses questions about the long-term impact of SANS on future human spaceflight missions. Areas Covered: In this review, we explore the current understanding of SANS including the different proposed etiologies and comparable terrestrial analogs. A systematic but selective review of literature published about SANS and related ocular diseases was conducted. Databases searched include PubMed and Scopus. This information was used to generate a review on potential mechanisms and analogs related to SANS. Expert Opinion: This review discusses the current status and future directions for SANS research, the role private space companies play in increasing access to space flight, and the possibility of future high-quality human spaceflight research in microgravity. We hope that the work on SANS can inspire technological innovation, increase our knowledge of terrestrial disorders, and possibly creating downstream spin-off technologies that have wider applications beyond space flight alone.