title: Reversible Increase of Central Choroidal Thickness During High-Altitude Exposure.
abstract: OBJECTIVE
  This study aimed to quantify the impact of high altitude on choroidal thickness and relate changes of altered choroidal blood flow to clinical parameters and acute mountain sickness (AMS). This work is related to the Tübingen High Altitude Ophthalmology (THAO) study.
  
  
  METHODS
  Enhanced depth imaging spectral-domain optical coherence tomography was used to quantify macular choroidal layer thickness. Peripheral oxygen saturation, heart rate, and AMS scores were assessed in eight healthy subjects at baseline (altitude, 341 m) and at altitude (4559 m) for respective correlations.
  
  
  RESULTS
  Longitudinal analysis revealed a significant (P = 0.011, ANOVA) increase in central choroidal thickness (CCT) during altitude exposure (CCT baseline = 271 ± 9 μm; CCT altitude = 288 ± 9 μm) due to an increased choroidal blood flow. Incidence of AMS at altitude was 50%, peripheral oxygen saturation decreased by 25%, and heart rate increased by 39%. All changes were completely reversible after descent to low altitudes.
  
  
  CONCLUSIONS
  A small but significant increase in choroidal thickness was observed upon acute altitude exposure to 4559 m. This increase in choroidal blood flow was not related to AMS and was fully reversible after return to low altitude.
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany 2Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom.
authors.forename: M Dominik
authors.initials: MD
authors.lastname: Fischer
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany 3Department of Ophthalmology, Katharinenhospital, Stuttgart, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schatz
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany.
authors.forename: Immanuel P
authors.initials: IP
authors.lastname: Seitz
authors.affiliation: University Medical Centre, I. Medical Department, Mannheim, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Schommer
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany.
authors.forename: Karl U
authors.initials: KU
authors.lastname: Bartz-Schmidt
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany 3Department of Ophthalmology, Katharinenhospital, Stuttgart, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany 3Department of Ophthalmology, Katharinenhospital, Stuttgart, Germany.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Willmann
mesh_terms: D000328:Adult; D000532:Altitude Sickness / Q000503:physiopathology*; D002829:Choroid / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D041623:Tomography, Optical Coherence
chemical_list: D010100:Oxygen