New insights into changes in corneal thickness in healthy mountaineers during a very-high-altitude climb to Mount Muztagh Ata.
OBJECTIVE
To investigate the effect of very high altitude and different ascent profiles on central corneal thickness (CCT).


METHODS
Twenty-eight healthy mountaineers were randomly assigned to 2 different ascent profiles during a medical research expedition to Mount Muztagh Ata (7546 m) in western China. Group 1 was allotted a shorter acclimatization time prior to ascent to 6265 m. The main outcome measure was CCT. Secondary outcome measures were oxygen saturation (SpO(2)) and symptom assessments of acute mountain sickness (cerebral acute mountain sickness score). Examinations were performed at 490, 4497, 5533, and 6265 m.


RESULTS
Central corneal thickness increased in both groups with increasing altitude and decreased after descent. In group 1 (with the shorter acclimatization), mean CCT increased from 537 to 572 microm. Mean CCT in group 2 increased from 534 to 563 microm (P = .048). The amount of decrease in SpO(2) paralleled the increase in CCT. There was no significant decrease in visual acuity. There was a significant correlation between CCT and cerebral acute mountain sickness score when controlled for SpO(2) and age.


CONCLUSIONS
Corneal swelling during high-altitude climbs is promoted by low SpO(2). Systemic delivery of oxygen to the anterior chamber seems to play a greater role in corneal oxygenation than previously thought. Adhering to a slower ascent profile results in less corneal edema. Visual acuity in healthy corneas is not adversely affected by edema at altitudes of up to 6300 m. Individuals with more acute mountain sickness-related symptoms had thicker corneas, possibly due to their higher overall susceptibility to hypoxia.
Bosch
Martina Monika
MM
Department of Ophthalmology, University Hospital Zurich, Frauenklinikstrasse 24, 8091 Zurich, Switzerland. martina.boesch@usz.ch
Barthelmes
Daniel
D
Merz
Tobias Michael
TM
Knecht
Pascal Bruno
PB
Truffer
Frederic
F
Bloch
Konrad E
KE
Thiel
Michael A
MA
Petrig
Benno L
BL
Turk
Alexander J
AJ
Schoch
Otto D
OD
Hefti
Urs
U
Landau
Klara
K
D000064:Acclimatization; D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000503:physiopathology*; D001274:Atmospheric Pressure; D003315:Cornea / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D015715:Corneal Edema / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009051:Mountaineering / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D011446:Prospective Studies; D014463:Ultrasonography; D014792:Visual Acuity / Q000502:physiology