title: Trichromatic and dichromatic relative sensitivity to green light in a mild hypoxic environment.
abstract: BACKGROUND
  Several studies have reported that individuals with normal color vision have a relative decrease in sensitivity to green light in hypoxic environments approximating altitudes above 4000 m. Because there is little available information describing the effects of mild hypoxic environments (less than 4000 m) in subjects with deficient color-vision, we examined the effect of mild hypoxia on the relative sensitivity to green light for color-normal and color-deficient subjects.
  
  
  METHODS
  Relative sensitivity to the green light was measured using the Medmont C-100 at ground and 3780 m in an altitude chamber. There were 30 subjects, 13 with normal color vision and 17 with a congenital red-green defect, who participated in the study. The relative sensitivity to the green light was determined from the average of four settings measured during the 4.5-h trial.
  
  
  RESULTS
  Color-normals and anomalous trichromats showed a small decrease in the relative sensitivity to the green light at 3780 m compared to ground. In contrast to the trichromatic results, the relative sensitivity of the dichromats to the green light did not differ between 3780 m and ground.
  
  
  CONCLUSIONS
  Our results show that a decrease in the relative sensitivity to green light can occur in hypoxic environments that are equivalent to altitudes greater than 3700 m in individuals with trichromatic but not dichromatic color vision. Although the change in sensitivity was significant, it was small and unlikely to have any operational impact.
authors.affiliation: School of Optometry, University of Waterloo, Waterloo, ON, Canada. jhovis@uwaterloo.ca
authors.forename: Jeffery K
authors.initials: JK
authors.lastname: Hovis
authors.forename: Nelda J
authors.initials: NJ
authors.lastname: Milburn
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Nesthus
mesh_terms: D000293:Adolescent; D000328:Adult; D000531:Altitude; D055253:Color Vision; D003117:Color Vision Defects / Q000453:epidemiology*; D006801:Humans; D000860:Hypoxia / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012684:Sensory Thresholds; D055815:Young Adult