title: Effects on colour discrimination during long term exposure to high altitudes on Mt Everest.
abstract: OBJECTIVE
  To investigate changes in colour discrimination as a result of chronic hypoxic exposure induced by extreme altitudes (above 8000 m) during an expedition to Mt Everest.
  
  
  METHODS
  Colour discrimination thresholds for tritan, protan and deutan axes were measured extensively in two male participants (four eyes) during an expedition to Mt Everest, using a quantitative, computer controlled psychophysical colour vision test (modified version of the Cambridge Colour Test). The tests were carried out over a period of 54 days at altitudes of 1300 m, 3450 m, 4410 m, 5060 m, 5300 m, 6450 m, 7200 m and 8000 m.
  
  
  RESULTS
  Colour vision tests 1 week before and 6 months after the expedition indicated normal colour discrimination in both participants. With increasing altitude, colour discrimination thresholds were found to rise, predominantly for the tritan (blue) axes in both observers. Deutan (green) thresholds were minimally elevated at high altitude, whereas protan (red) was altered in one observer. Tritan colour discrimination thresholds decreased as a function of time spent at a given altitude and normalised upon return to low altitude.
  
  
  CONCLUSIONS
  Chronic hypoxia induced by high altitude exposure transiently affects colour discrimination, in particular tritan axis discrimination. Decreased tritan discrimination is partly reversible upon physiological adaptation to high altitude and completely normalised upon return to low altitude.
authors: Eye Hospital, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Schleichstrasse 12-16, Germany. gabriel.willmann@med.uni-tuebingen.de
authors: Gabriel
authors: G
authors: Willmann
authors: Iliya V
authors: IV
authors: Ivanov
authors: Manuel D
authors: MD
authors: Fischer
authors: Sukhamay
authors: S
authors: Lahiri
authors: Rohit K
authors: RK
authors: Pokharel
authors: Annette
authors: A
authors: Werner
authors: Tejvir S
authors: TS
authors: Khurana
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000531:Altitude; D002908:Chronic Disease; D003118:Color Perception / Q000502:physiology*; D003119:Color Perception Tests; D003117:Color Vision Defects / Q000503:physiopathology*; D004781:Environmental Exposure; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009051:Mountaineering / Q000502:physiology*; D012044:Regression Analysis; D013997:Time Factors