title: Visual fields during acute exposure to a simulated altitude of 7620 m.
abstract: BACKGROUND
  The hypoxia associated with sudden exposure to high altitude is known to impair vision and may thereby affect flight safety. However, no data were available regarding hypoxic effects on visual fields. The aim of this study was to evaluate black-and-white visual field sensitivity with acute hypoxia during acute exposure to a simulated altitude of 7620 m.
  
  
  METHODS
  Subjects were 15 male pilots 26-39 yr of age. We measured arterial oxygen saturation (S(aO2)%) using transdermal pulse oximetry while the visual field was measured within a 30 degrees eccentricity in the right eye by computerized perimetry. The subject breathed 100% O2 for 30 min before and during chamber ascent, then removed his mask while measurements were performed.
  
  
  RESULTS
  The S(aO2)% and visual field sensitivities (mean +/- SD) at ground level were 99.1 +/- 0.4% and 43.9 +/- 2.1 dB, respectively. During hypoxia, the S(aO2)% dropped to 64.0 +/- 5.4% within 3 min. Mean visual sensitivity was significantly reduced by 7.2 +/- 1.6 dB. Furthermore, peripheral sensitivity was slightly but significantly more diminished than central sensitivity.
  
  
  CONCLUSIONS
  Severe acute hypoxia reduces central and moderate peripheral black-and-white vision by a factor of two with the strongest effect in the periphery.
authors.affiliation: Department of Ophthalmology, Kaohsiung Armed Force General Hospital, Kaohsiung, Taiwan.
authors.forename: Chi-Ting
authors.initials: CT
authors.lastname: Horng
authors.forename: Chun-Cheng
authors.initials: CC
authors.lastname: Liu
authors.forename: Der-Min
authors.initials: DM
authors.lastname: Wu
authors.forename: Yi-Chang
authors.initials: YC
authors.lastname: Wu
authors.forename: Jiann-Torng
authors.initials: JT
authors.lastname: Chen
authors.forename: Cheng-Jong
authors.initials: CJ
authors.lastname: Chang
authors.forename: Ming-Ling
authors.initials: ML
authors.lastname: Tsai
mesh_terms: D000208:Acute Disease; D000328:Adult; D000337:Aerospace Medicine; D000531:Altitude; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood; D058609:Visual Field Tests; D014794:Visual Fields
chemical_list: D010100:Oxygen