title: Intraocular pressure is not associated with acute mountain sickness.
abstract: OBJECTIVE
  Acute mountain sickness (AMS) is common at high altitude and may lead to high altitude cerebral edema (HACE) if not properly recognized. Previous studies have suggested that AMS is associated with increases in intracranial pressure (ICP). Increased ICP has been associated with increased intra-ocular pressure (IOP). This study was designed to determine the association between IOP and AMS.
  
  
  METHODS
  Subjects were recruited from a convenience sample of travelers in the Khumbu region of Nepal, elevation 14,410 ft (4392 m). Study participation involved completion of a questionnaire to assess for AMS by the Lake Louise Score (LLS), followed by three IOP measurements in each eye. Investigators were blinded to the LLS. Subjects with a history of ocular surgery were excluded. Three IOP measurements per eye were made using an applanation tonometer (Tono-Pen XL(®), Reichart Technologies) and averaged across both eyes. Multivariable logistic regression analysis was used to estimate the association between IOP and AMS while adjusting for age, ascent or descent, and use of acetazolamide. IOP and blood O2 saturation were compared using a Spearman correlation coefficient.
  
  
  RESULTS
  161 subjects were enrolled with a median age of 36 (IQR: 29-45) years; 60% were male, 75% were ascending, and 64% were taking acetazolamide; additionally, 38%, (95% CI: 31%-47%) were diagnosed with AMS (LLS ≥3). The median IOP was 21 (IQR 18-24) mmHg. The logistic regression model demonstrated no association between IOP and AMS as measured by LLS (odds ratio [OR] 1.0, 95% CI: 0.9-1.1),age (OR 1.0, 95% CI: 0.9-1.0) or with use of acetazolamide (OR 1.4, 95% CI: 0.6-2.6). Ascent (OR 0.4, 95% CI: 0.2-0.9) was negatively associated with IOP but not significantly so. IOP and O2 saturation were not correlated (p=0.93).
  
  
  CONCLUSIONS
  IOP measured at high altitude is not associated with the diagnosis of AMS. Other approaches to diagnose AMS easily and accurately are needed.
authors.affiliation: 1 Department of Emergency Medicine, Denver Health Medical Center , Denver, Colorado.
authors.forename: Tracy
authors.initials: T
authors.lastname: Cushing
authors.forename: Ryan
authors.initials: R
authors.lastname: Paterson
authors.forename: Jason
authors.initials: J
authors.lastname: Haukoos
authors.forename: N Stuart
authors.initials: NS
authors.lastname: Harris
mesh_terms: D000086:Acetazolamide / Q000627:therapeutic use; D000208:Acute Disease; D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood / Q000503:physiopathology* / Q000517:prevention & control; D002257:Carbonic Anhydrase Inhibitors / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects / Q000502:physiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D016037:Single-Blind Method; D011795:Surveys and Questionnaires; D014065:Tonometry, Ocular
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D000086:Acetazolamide; D010100:Oxygen