title: Neuro-Ophthalmology of Space Flight.
abstract: BACKGROUND
  To describe the history, clinical findings, and possible pathogenic etiologies of the constellation of neuro-ophthalmic findings discovered in astronauts after long-duration space flight and to discuss the terrestrial implications of such findings.
  
  
  METHODS
  Retrospective review of published observational, longitudinal examination of neuro-ophthalmic findings in astronauts after long-duration space flight; analysis of postflight questionnaires regarding in-flight vision changes in approximately 300 additional astronauts; and hypothesis generating for developing possible future countermeasures and potential implications for neuro-ophthalmic disorders on Earth. Astronauts with neuro-ophthalmic findings, which were not present at the start of a space flight mission and only seen on return from long-duration space missions to the International Space Station, will be discussed.
  
  
  RESULTS
  After 6 months of space flight, 7 astronauts had ophthalmic findings consisting of optic disc edema in 5, globe flattening in 5, choroidal folds in 5, cotton-wool spots in 3, nerve fiber layer thickening detected by optical coherence tomography in 6, and decreased near vision in 6. Five of 7 astronauts with near vision complaints had a hyperopic shift ≥+0.50 diopters (D) between pre-/post-mission spherical equivalent refraction in 1 or both eyes (range, +0.50 to +1.75 D). These 5 astronauts showed globe flattening on magnetic resonance imaging. A total of 6 lumbar punctures have been performed to date (4 in the originally described cohort) and documented opening pressures of 18, 22, 21, 21.5, 28, and 28.5 cm H2O. These were performed at 8, 66, 19, 7, 12, and 57 days after mission, respectively. The 300 postflight questionnaires documented that approximately 29% and 60% of astronauts on short-duration and long-duration missions, respectively, experienced a degradation in distant and near visual acuity. Some of these vision changes remain unresolved for years after flight. Several possible pathogenic mechanisms, as well as potential countermeasures and discussion of possible terrestrial implications, are described.
  
  
  CONCLUSIONS
  We previously hypothesized that the optic nerve and ocular changes that we described in astronauts may be the result of orbital and cranial cephalad fluid shifts brought about by prolonged microgravity exposure. The findings we reported previously and continue to see in astronauts may represent parts of a spectrum of ocular and cerebral responses to extended microgravity exposure. Future investigations hopefully will lead to countermeasures that can be used to eliminate or lessen the magnitude of these potentially harmful findings before long-duration space flight including the possibility of a manned mission to Mars.
authors.affiliation: Department of Ophthalmology (AGL, CRB), Houston Methodist Hospital, Houston, Texas; Department of Ophthalmology (AGL), Baylor College of Medicine, Houston, Texas; Departments of Ophthalmology, Neurology, and Neurosurgery (AGL), Weill Cornell Medical College, New York, New York; Department of Ophthalmology (AGL), The University of Texas Medical Branch, Galveston, Texas; Department of Ophthalmology (AGL), The University of Iowa Hospitals and Clinics, Iowa City, Iowa; Section of Ophthalmology (AGL), The University of Texas MD Anderson Cancer Center, Houston, Texas; Space Medicine Division (WJT, SFH), National Aeronautics and Space Administration, Washington, DC; US Army (THM), Cooper Landing, Alaska; Coastal Eye Associates (CRG), Webster, Texas; and Universities Space Research Association (CO), National Aeronautics and Space Administration, Washington, DC.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Lee
authors.forename: William J
authors.initials: WJ
authors.lastname: Tarver
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Mader
authors.forename: Charles Robert
authors.initials: CR
authors.lastname: Gibson
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Hart
authors.forename: Christian A
authors.initials: CA
authors.lastname: Otto
mesh_terms: D018480:Astronauts; D002555:Cerebrospinal Fluid / Q000502:physiology; D015862:Choroid Diseases / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D006956:Hyperopia / Q000209:etiology* / Q000503:physiopathology; D019586:Intracranial Hypertension / Q000503:physiopathology; D010211:Papilledema / Q000209:etiology* / Q000503:physiopathology; D012189:Retrospective Studies; D013026:Space Flight; D014786:Vision Disorders / Q000209:etiology* / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology; D014893:Weightlessness / Q000009:adverse effects*