Modification of colour vision in the green/red axis in acute and chronic hypoxia explored with a portable anomaloscope.

The effects of acute (4350 m), subacute (4800 m) and chronic (4800 m) altitude hypoxia on colour vision in the green/red axis were explored in eight sea-level natives by means of a simple portable anomaloscope. Subjects were required to create a yellow colour from a mixture of red (635 nm) and green (565 nm) obtained from two electroluminescent diodes. A relative decrease in green, compared to red, sensitivity was observed in each hypoxic condition (p less than 0.001). Acclimatization to altitude, evidenced by the improvement of arterial O2 saturation (earoximeter) was accompanied by a slight but not significant return to normal colour sensitivities. The influence of factors such as fatigue, season, and age is discussed and does not seem likely to account for the observed variations.