The effects of high altitude on central corneal thickness

Purpose A large number of people are exposed to long‐term hypobaric hypoxic conditions via mountaineering, skiing and trekking. Other people such as aviators and high‐altitude parachutists are exposed to short‐term hypobaric hypoxic conditions. It is known that hypobaric conditions alter physiological and morphological status of the eye including the central corneal thickness (CCT). Our aim is to review the results of the influences of high altitude on CCT. We will also add our experience on the influences of short‐term hypobaric hypoxia on CCT. Methods Reports covering this topic will be discussed. The possible mechanisms for the alterations in CCT will be included. Hypobaric hypoxic conditions simulate high altitudinal environments, which was the basis of our study covering 70 eyes of 35 healthy men exposed to hypobaric hypoxic condition. We measured the CCT via ultrasound pachmetry at local ground (792 m above sea level) and then during short‐term hypobaric hypoxic exposure (equivalent 9144 m above). Results CCT has been found to be increased at high altitudes. We also found that hypobaric hypoxic condition increased the CCT significantly. The mechanism of increased CCT is not clear, although the alterations in corneal endothelial cells function seem to be the main explanation. Systemic delivery of oxygen to the anterior chamber can possibly be an important contributing factor based on a recent study. Conclusion CCT has been reported to be increased at high altitude. The possible underlying mechanisms are altered endothelial function and metabolic activity.