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Tobias Peters, Andreas Schatz, Max Schultheiss, Gabriel Willmann, Helmut Wilhelm, Barbara Wilhelm, Florian Gekeler, Pupil Research Group, Centre for Ophthalmology, University of Tübingen, Germany; Pupillography under Hypobaric Hypoxia- The THAO trial. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1934. doi: https://doi.org/.
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The results presented here are related to the THAO study (http://www.thao-project.com), dealing with acute mountain sickness (AMS) and ophthalmological effects of hypobaric hypoxia after fast ascent, both in regard to morphological and functional changes.
14 participants (age 25-54yrs) intended to reach the summit at Capanna Margherita (CM, Italy) within 24 hrs starting from 1635m up to CM at 4559m. More than 14 days before exposure to high altitude participants were not allowed to climb above 2000m. During day 1 to 4 an almost complete ophthalmological assessment including ERG, OCT, FLA, AF, and Pupillography was performed twice a day. The pupillograph used was a Computer intergrated Pupillograph (CiP by Amtech, Dossenheim Germany). The CiP provides a 585nm LED light source resulting in corneal illuminance of about 3lx. Stimulus length was set at 200ms. AMS was defined by the Lake Louise and the AMS-c score.
Ratios (value/value at baseline) of amplitude, latency, velocity, initial diameter and relative amplitude were calculated and plotted against day of condition. There was a significant result to higher amplitude and higher velocity of the pupillary light reaction and lower initial diameter in all participants in high altitude. The changes in pupillary parameters did not correlate with the AMS score.
Tolerance and adaptation to exposure to high altitude were different among participants. Results of pupillography showed clearly the influence by high altitude after fast ascent, the changes might be interpreted as indicators of an increased parasympathetic tone. Acute mountain sickness was not predictable or clearly detectable by means of pupillography.
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