title: Pupillary light reaction during high altitude exposure.
abstract: OBJECTIVE
  This study aimed to quantify the pupillary light reaction during high altitude exposure using the state of the art Compact Integrated Pupillograph (CIP) and to investigate a potential correlation of altered pupil reaction with severity of acute mountain sickness (AMS). This work is related to the Tübingen High Altitude Ophthalmology (THAO) study.
  
  
  METHODS
  Parameters of pupil dynamics (initial diameter, amplitude, relative amplitude, latency, constriction velocity) were quantified in 14 healthy volunteers at baseline (341 m) and high altitude (4559 m) over several days using the CIP. Scores of AMS, peripheral oxygen saturation and heart rate were assessed for respective correlations with pupil dynamics. For statistical analysis JMP was used and data are shown in terms of intra-individual normalized values (value during exposure/value at baseline) and the 95% confidence interval for each time point.
  
  
  RESULTS
  During high altitude exposure the initial diameter size was significantly reduced (p<0.05). In contrast, the amplitude, the relative amplitude and the contraction velocity of the light reaction were significantly increased (p<0.05) on all days measured at high altitude. The latency did not show any significant differences at high altitude compared to baseline recordings. Changes in pupil parameters did not correlate with scores of AMS.
  
  
  CONCLUSIONS
  Key parameters of the pupillary light reaction are significantly altered at high altitude. We hypothesize that high altitude hypoxia itself as well as known side effects of high altitude exposure such as fatigue or exhaustion after ascent may account for an altered pupillogram. Interestingly, none of these changes are related to AMS.
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany.
authors: Maximilian
authors: M
authors: Schultheiss
authors: Department of Sports Medicine of Medical Clinic, University of Heidelberg, Heidelberg, Germany.
authors: Kai
authors: K
authors: Schommer
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany ; Department of Ophthalmology, Katharinenhospital, Stuttgart, Germany.
authors: Andreas
authors: A
authors: Schatz
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany.
authors: Barbara
authors: B
authors: Wilhelm
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany.
authors: Tobias
authors: T
authors: Peters
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany ; Nuffield Laboratory of Ophthalmology Oxford, University of Oxford, Oxford, United Kingdom.
authors: M Dominik
authors: MD
authors: Fischer
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany.
authors: Eberhart
authors: E
authors: Zrenner
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany.
authors: Karl U
authors: KU
authors: Bartz-Schmidt
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany ; Department of Ophthalmology, Katharinenhospital, Stuttgart, Germany.
authors: Florian
authors: F
authors: Gekeler
authors: Center of Ophthalmology, University of Tübingen, Tübingen, Germany ; Department of Ophthalmology, Katharinenhospital, Stuttgart, Germany.
authors: Gabriel
authors: G
authors: Willmann
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology*; D012025:Reflex, Pupillary