Spaceflight Associated Neuro-ocular Syndrome (SANS) and its countermeasures

Tuan Nguyen¹, Joshua Ong², Tyson Brunstetter³, C Robert Gibson⁴, Brandon R Macias⁵, Steven Laurie⁵, Thomas Mader⁶, Alan Hargens⁷, Jay C Buckey⁸, Mimi Lan⁸, Peter Wostyn⁹, Cihan Kadipasaoglu¹⁰, Scott M Smith¹¹, Sara R Zwart¹², Benjamin J Frankfort¹³, Sarah Aman¹⁴, Jessica M Scott¹⁵, Ethan Waisberg¹⁶, Mouayad Masalkhi¹⁷, Andrew G Lee¹⁸

Affiliations

¹ Weill Cornell/Rockefeller/Sloan-Kettering Tri-Institutional MD-PhD Program, New York City, New York, USA.
² Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, MI, USA.
³ NASA Johnson Space Center, Houston, Texas, USA.
⁴ KBR, NASA Space Medicine Operations Division, Houston, TX, USA; South Shore Eye Center, League City, TX, USA.
⁵ KBR, NASA Space Medicine Operations Division, Houston, TX, USA.
⁶ NASA Ophthalmology Consultant, Moab, UT, USA.
⁷ Department of Orthopaedic Surgery, University of California, Altman Clinical and Translational Research Institute, La Jolla, CA, San Diego, USA.
⁸ Space Medicine Innovations Laboratory, Geisel School of Medicine at Dartmouth, One Medical Center Drive, Lebanon, NH, USA.
⁹ Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium.
¹⁰ Department of Neurology, Houston Methodist Hospital, Houston, TX, USA.
¹¹ Human Health and Performance Directorate, NASA Johnson Space Center, Houston, TX, USA.
¹² University of Texas Medical Branch, Galveston, TX, USA.
¹³ Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, TX, USA.
¹⁴ Wilmer Eye Institute, Johns Hopkins Medicine, Baltimore, MD, USA.
¹⁵ Memorial Sloan Kettering Cancer Center, Weill Cornell Medical College, New York, NY, USA.
¹⁶ University of Cambridge, Cambridge, United Kingdom.
¹⁷ University College Dublin School of Medicine, Belfield, Dublin, Ireland.
¹⁸ The Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX, USA; Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY, USA; Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA; University of Texas MD Anderson Cancer Center, Houston, TX, USA; Texas A&M College of Medicine, Bryan, TX, USA; Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA. Electronic address: aglee@houstonmethodist.org.

PMID: 39971096
PMCID: PMC12103276 (available on 2026-05-01)
DOI: 10.1016/j.preteyeres.2025.101340

Review

Spaceflight Associated Neuro-ocular Syndrome (SANS) and its countermeasures

Tuan Nguyen et al. Prog Retin Eye Res. 2025 May.

. 2025 May:106:101340.

doi: 10.1016/j.preteyeres.2025.101340. Epub 2025 Feb 17.

Authors

Affiliations

¹ Weill Cornell/Rockefeller/Sloan-Kettering Tri-Institutional MD-PhD Program, New York City, New York, USA.
² Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, MI, USA.
³ NASA Johnson Space Center, Houston, Texas, USA.
⁴ KBR, NASA Space Medicine Operations Division, Houston, TX, USA; South Shore Eye Center, League City, TX, USA.
⁵ KBR, NASA Space Medicine Operations Division, Houston, TX, USA.
⁶ NASA Ophthalmology Consultant, Moab, UT, USA.
⁷ Department of Orthopaedic Surgery, University of California, Altman Clinical and Translational Research Institute, La Jolla, CA, San Diego, USA.
⁸ Space Medicine Innovations Laboratory, Geisel School of Medicine at Dartmouth, One Medical Center Drive, Lebanon, NH, USA.
⁹ Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium.
¹⁰ Department of Neurology, Houston Methodist Hospital, Houston, TX, USA.
¹¹ Human Health and Performance Directorate, NASA Johnson Space Center, Houston, TX, USA.
¹² University of Texas Medical Branch, Galveston, TX, USA.
¹³ Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, TX, USA.
¹⁴ Wilmer Eye Institute, Johns Hopkins Medicine, Baltimore, MD, USA.
¹⁵ Memorial Sloan Kettering Cancer Center, Weill Cornell Medical College, New York, NY, USA.
¹⁶ University of Cambridge, Cambridge, United Kingdom.
¹⁷ University College Dublin School of Medicine, Belfield, Dublin, Ireland.
¹⁸ The Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX, USA; Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY, USA; Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA; University of Texas MD Anderson Cancer Center, Houston, TX, USA; Texas A&M College of Medicine, Bryan, TX, USA; Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA. Electronic address: aglee@houstonmethodist.org.

PMID: 39971096
PMCID: PMC12103276 (available on 2026-05-01)
DOI: 10.1016/j.preteyeres.2025.101340

Abstract

Astronauts can develop a distinct collection of neuro-ophthalmic findings during long duration spaceflight, collectively known as Spaceflight Associated Neuro-ocular Syndrome (SANS). These clinical characteristics include optic disc edema, hyperopic refractive shifts, globe flattening, and chorioretinal folds, which may pose a health risk for future space exploration. Obtaining knowledge of SANS and countermeasures for its prevention is crucial for upcoming crewed space missions and warrants a multidisciplinary approach. This review examines the potential causes and countermeasures of SANS, including space anticipation glasses, lower body negative pressure, venoconstrictive thigh cuffs, impedance threshold devices, translaminar pressure gradient modulation, centrifugation, artificial gravity, pharmaceuticals, and precision nutritional supplementation. This paper highlights future research directions for understanding the genetic, anthropometric, behavioral, and environmental susceptibilities to SANS as well as how to use terrestrial analogs for testing future mitigation strategies.

Keywords: Genetics; Goggles; LBNP; Lower body negative pressure; One-carbon metabolism; SANS; Spaceflight associated neuro-ocular syndrome; Venous thigh cuffs.

PubMed Disclaimer

Conflict of interest statement

Declaration of competing interest Andrew G. Lee, MD is a consultant for the National Aeronautics and Space Administration (NASA).

References

1. Alfrey CP, Udden MM, Leach-Huntoon C, Driscoll T, Pickett MH, 1996. Control of red blood cell mass in spaceflight. J Appl Physiol (1985) 81, 98–104. - PubMed
1. Alperin N, Bagci A, Lam B, Sklar E, 2013. Automated quantitation of the posterior scleral flattening and optic nerve protrusion by MRI in idiopathic intracranial hypertension. American Journal of Neuroradiology 34, 2354–2359. - PMC - PubMed
1. Alperin N, Bagci AM, 2018. Spaceflight-induced visual impairment and globe deformations in astronauts are linked to orbital cerebrospinal fluid volume increase, Intracranial pressure & neuromonitoring XVI. Springer, pp. 215–219. - PubMed
1. Alperin N, Bagci AM, Lee SH, 2017. Spaceflight-induced changes in white matter hyperintensity burden in astronauts. Neurology 89, 2187–2191. - PubMed
1. Altholz J, Bocobo G, Singh G, Mason S, Young M, Oswald T, Osborne S, Van Baalen MG, Gibson C, Tarver WJ, Tsung A, Brunstetter T, 2024. Effect of Spaceflight on Refractive Error & Axial Length: Implications for Spaceflight Associated Neuro-Ocular Syndrome (SANS), 94th Annual Scientific Mtg, Aerospace Medical Association, Chicago, IL.

REFERENCES Table 2

1. Laurie SS, Greenwald SH, Marshall-Goebel K, Pardon LP, Gupta A, Lee SMC, Stern C, Sangi-Haghpeykar H, Macias BR, Bershad EM, 2021. Optic disc edema and chorioretinal folds develop during strict 6° head-down tilt bed rest with or without artificial gravity. Physiological Reports 9, e14977. - PMC - PubMed
1. Laurie SS, Lee SMC, Macias BR, Patel N, Stern C, Young M, Stenger MB, 2020. Optic Disc Edema and Choroidal Engorgement in Astronauts During Spaceflight and Individuals Exposed to Bed Rest. JAMA Ophthalmology 138, 165–172. - PMC - PubMed
1. Laurie SS, Macias BR, Dunn JT, Young M, Stern C, Lee SMC, Stenger MB, 2019. Optic Disc Edema after 30 Days of Strict Head-down Tilt Bed Rest. Ophthalmology 126, 467–468. - PubMed
1. Laurie SS, Vizzeri G, Taibbi G, Ferguson CR, Hu X, Lee SMC, Ploutz-Snyder R, Smith SM, Zwart SR, Stenger MB, 2017. Effects of short-term mild hypercapnia during head-down tilt on intracranial pressure and ocular structures in healthy human subjects. Physiological Reports 5, e13302–e13302. - PMC - PubMed
1. Sater SH, Sass AM, Rohr JJ, Marshall-Goebel K, Ploutz-Snyder RJ, Ethier CR, Stenger MB, Kramer LA, Martin BA, Macias BR, 2021. Automated MRI-based quantification of posterior ocular globe flattening and recovery after long-duration spaceflight. Eye (Lond) 35, 1869–1878. - PMC - PubMed

Publication types

Actions

MeSH terms

Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions

Grants and funding

LinkOut - more resources

Full Text Sources
- Elsevier Science
- Ovid Technologies, Inc.
Medical
- MedlinePlus Consumer Health Information
- MedlinePlus Health Information

Save citation to file

Email citation

Add to Collections

Add to My Bibliography

Your saved search

Create a file for external citation management software

Your RSS Feed

Spaceflight Associated Neuro-ocular Syndrome (SANS) and its countermeasures

Affiliations

Spaceflight Associated Neuro-ocular Syndrome (SANS) and its countermeasures

Authors

Affiliations

Abstract

Conflict of interest statement

References

REFERENCES Table 2

Publication types

MeSH terms

Grants and funding

LinkOut - more resources

Full Text Sources

Medical