NPJ Microgravity · 5 authors, 13 centres
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This narrative review synthesizes translational research on Spaceflight Associated Neuro-ocular Syndrome (SANS), covering ocular and brain structural changes in microgravity, intracranial pressure mechanisms, and candidate countermeasures. It identifies long-term low-level lower body negative pressure (LBNP) as the most promising countermeasure while highlighting critical knowledge gaps in SANS etiology and management.
This narrative review examines the eye-brain axis under microgravity conditions, focusing on Spaceflight Associated Neuro-ocular Syndrome (SANS). SANS findings include globe flattening, hyperopic refractive error shift, optic nerve sheath distension, optic disc edema, choroidal and retinal folds, and cotton wool spots. The review discusses intracranial pressure elevation due to headward fluid shift as a proposed mechanism, while noting that ground-based studies including direct ICP recording during exercise with elevated CO2 demonstrated no pathological elevation in ICP. Multiple countermeasures are evaluated: long-term low-level LBNP is identified as the most promising candidate, having shown amelioration of early SANS signs in bedrest studies; venous-constrictive thigh cuffs demonstrated a 20% reduction in internal jugular venous diameter but ground-based ICP measurements showed no significant reductions; dry immersion produced rapid increases in optic nerve sheath diameter.
