Research progress on spaceflight associated neuro-ocular syndrome,ground simulation experiments and countermeasures
Spaceflight associated neuro-ocular syndrome(SANS)refers to a series of ocular,neurological and neuroimaging manifestations observed in astronauts during and after long-term space flight,including optic disc edema,posterior globe flattening,choroid-retinal folds,and hyperopic refractive shift.These effects may have short-term or long-term on vision,cognition and other aspects of astronauts'health.Therefore,elucidating the pathogenesis of SANS,conducting effective ground simulation experiments,and developing corresponding mitigation strategies are crucial for enabling deeper and longer-duration space exploration.Current understanding of the pathogenesis of SANS includes increased intracranial pressure,fluctions in cerebral blood volume and vascular remodeling,upward displacement of the brain and optic chiasm,imbalance in ocular lymphatic system flow,cytotoxic edema,and orbital fat swelling,etc.Among the various ground simulation experiment,the 6 ° head-down tilt bed rest has been extensively studied and has been shown to replicate various manifestations of SANS,such as optic nerve sheath expansion,retinal nerve layer thickening,choroidal thickness increase and optic disc edema.Additionally,dry immersion and parabolic flight have also demonstrated some aspects of SANS during ground simulation experiments.The use of lower body negative pressure has been identified as a potential countermeasure to reduce choroidal thickening and increase in optic nerve sheath diameter.Furthermore,positive pressure goggles are also expected to be an effective strategy for mitigating the effects of SANS.This article provides a comprehensive review of the relevant advancements in the field of SANS,both domestically and internationally.
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