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G. Willmann, I. Ivanov, M. D. Fischer, R. K. Pokharel, S. Lahiri, T. S. Khurana, A. Werner; Specific Impairment in Blue Discrimination During an Ascent of Mt. Everest. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2730.
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Hypoxia is known to alter a number of CNS functions including visual functions. In this study, we investigated changes in color discrimination for tritan, deutan and protan axes as a result of extreme natural hypobaric hypoxia at different altitudes during a medical research expedition into the 'death zone' (above 8000 m) on Mt. Everest 8850m, Nepal.
The Mt. Everest hypoxia research expedition in May 2008 consisted of two members (ages 31 and 46 yrs). The subjects were tested for color vision discrimination along the tritan/deutan and protan axes in color space using the Cambridge Colour Test (Cambridge Research Systems, Cambridge, UK) over a period of 50 days at various altitudes. The stimuli were presented on a calibrated LCD screen (Asus Eee) at 8 degrees of visual angle in a dark tent 4 hours after sunset. The measurments were taken at heights of 3450m, 4410m, 4820m post 5300m, 5300m, 6470m, 7100m and 6470m post 8400m. Control measurements were taken 4 weeks and 6 months after the expedition at 50m.
Complete data records of two participants (4 eyes) were analyzed. In both mountaineers a consistent and significant rise of the tritan color discrimination threshold with increased altitude exposure was observed. However, deutan and protan thresholds remained within normal limits.
We investigated the effects of extreme natural hypobaric hypoxia on color discrimination over a 50-day period using a psychophysical vision test. We conclude, that hypobaric hypoxia results in a decrease in color discrimination along the tritan (blue/yellow) axis with increasing altitude. No impairments were noted in the red and green ranges.
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