title: What happens to intraocular pressure at high altitude?
abstract: OBJECTIVE
  To investigate changes of intraocular pressure on ascent to high altitude.
  
  
  METHODS
  The Apex 2 medical research expedition provided the opportunity to measure intraocular pressure (IOP) and central corneal thickness (CCT) in 76 healthy lowlanders. They all arrived in La Paz, Bolivia (altitude, 3700 m), where they spent 4 days before being driven more than 2 hours to the Cosmic Physics Laboratory at Chacaltaya (5200 m) where they stayed for 7 days. IOP and CCT were measured with a hand-held tonometer and ultrasound pachymetry on the first, third, and seventh days at 5200 m. Pre- and postexpedition CCT and postexpedition IOP readings at sea-level were also measured.
  
  
  RESULTS
  IOP increased significantly from baseline after acute exposure to altitude before returning to baseline with time. IOP at baseline, change in IOP from baseline, and IOP at altitude did not predict symptoms of acute mountain sickness (AMS) or development of high-altitude retinopathy (HAR).
  
  
  CONCLUSIONS
  Acute exposure to altitude caused a statistically significant but clinically insignificant increase in IOP. This finding may be partially explained by the change in CCT. IOP returned to baseline levels and possibly lower with prolonged exposure to altitude. Changes in IOP at altitude are not predictive of symptoms of acute mountain sickness (AMS) or development of high-altitude retinopathy (HAR).
authors: Tennent Institute of Ophthalmology, Gartnavel General Hospital, 1053 Great Western Road, Glasgow, Scotland, UK. john@somner.org.uk
authors: John E A
authors: JE
authors: Somner
authors: Daniel S
authors: DS
authors: Morris
authors: Kirsten M
authors: KM
authors: Scott
authors: Ian J C
authors: IJ
authors: MacCormick
authors: Peter
authors: P
authors: Aspinall
authors: Baljean
authors: B
authors: Dhillon
mesh_terms: D000293:Adolescent; D000328:Adult; D000531:Altitude; D001274:Atmospheric Pressure; D003315:Cornea / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D033401:Microscopy, Acoustic; D008875:Middle Aged; D014065:Tonometry, Ocular