Visual fields during acute exposure to a simulated altitude of 7620 m.
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.
Horng
Chi-Ting
CT
Department of Ophthalmology, Kaohsiung Armed Force General Hospital, Kaohsiung, Taiwan.
Liu
Chun-Cheng
CC
Wu
Der-Min
DM
Wu
Yi-Chang
YC
Chen
Jiann-Torng
JT
Chang
Cheng-Jong
CJ
Tsai
Ming-Ling
ML
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
D010100:Oxygen