title: Saccadic velocity and pupillary reflexes during acclimatization to altitude (4300 m).
abstract: BACKGROUND
  Oculometrics have been shown to be responsive to acute hypoxemia. We investigated whether oculometrics could be used as an objective index of a hypoxic effect on the central nervous system (CNS) during altitude acclimatization. We hypothesized that oculomotor reflexes [pupil diameter (PD), constriction amplitude (CA), constriction latency (CL), and saccadic velocity (SV)] changed in concert with a select number of accepted acclimatization variables and that these changes correlated with the severity of acute mountain sickness (AMS).
  
  
  METHODS
  After sea-level, baseline (SLB) measurements were obtained, 18 men (19-33 yr) were transported to Pikes Peak, CO (4300 m), where they remained for 14 d. Periodic measurements (days 1-4, 6, 7, 9, 10, and 12) were made of PD, CA, CL, and SV in addition to heart rate (HR), pulse oximetry (SpO2), end-tidal PO2 and PCO2, 24-h urinary catecholamine concentrations, and AMS severity (environmental symptoms questionnaire, ESQ).
  
  
  RESULTS
  PD and CL decreased from SLB on days 1-4 and subsequently returned toward SLB; these changes paralleled changes in ventilatory and circulatory variables. CA decreased on days 1 and 2 and remained decreased for 12 d. SV increased over days 1-6 then returned toward SLB with continued exposure, similar to changes in urinary catecholamines. With acclimatization, CL correlated with HR and SpO2; SV correlated with PCO2, HR, and SpO2. AMS severity peaked during days 2-4, returned toward SLB over the next 10 d, and correlated only with CL (p = 0.045).
  
  
  CONCLUSIONS
  Oculometrics can be used as an indicator of CNS hypoxia and altitude acclimatization, although there was no strong correlation with AMS severity.
authors: U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007, USA. allen.cymerman@us.army.mil
authors: Allen
authors: A
authors: Cymerman
authors: Stephen R
authors: SR
authors: Muza
authors: Anne L
authors: AL
authors: Friedlander
authors: Charles S
authors: CS
authors: Fulco
authors: Paul B
authors: PB
authors: Rock
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000208:Acute Disease; D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000532:Altitude Sickness / Q000503:physiopathology*; D001274:Atmospheric Pressure; D006801:Humans; D008297:Male; D008889:Military Personnel; D011680:Pupil / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D011795:Surveys and Questionnaires; D013997:Time Factors