Neuro-Ophthalmology of Outer Space

Physiologic and pathologic systemic responses and novel but dramatic ocular changes are known to occur in the microgravity environment of outer space. The precise effects of the long duration space flight environment on the human eye and brain remain ill-defined but over the last decade, the United States National Aeronautics and Space Administrations (NASA) Space Medicine Division has documented varying degrees of optic disc edema, globe flattening, choroidal folds, cotton wool spots (CWS), and hyperopic refractive error shifts in astronauts during and after long-duration space flight. In addition, neuroradiographic and ultrasonographic findings have demonstrated structural correlates to the clinical findings experienced by our long duration space flyers including flattening of the posterior globe and increased cerebrospinal fluid signal in the optic nerve sheaths. Although there have been some similarities of these radiographic and neuro-ophthalmic clinical findings with terrestrial idiopathic intracranial hypertension (IIH), there have also been clear differences.