According to a report in the February issue of Archives of Ophthalmology swelling commonly occurs in the corneas of mountain climbers, but does not appear to affect vision at altitudes of up to 6,300 meters (about 20,670 feet).
“High-altitude mountaineering is a popular recreational sport among healthy lowlanders,” the authors write as background information in the article. “As a consequence of the exposure to hypobaric atmospheric conditions with a consecutive decrease in oxygen saturation, high-altitude climbing may lead to acute mountain sickness and the rare but potentially fatal high-altitude cerebral edema.” Changes to the cornea, the transparent membrane covering the front of the eye, also occur during high-altitude climbs.
The authors studied the effects of high-altitude climbing on corneal thickness among 28 healthy volunteers climbing Mount Muztagh Ata in western China. The mountaineers were randomly assigned to two different ascending paths, with one group being allotted a shorter time to acclimate before ascending to 6,265 meters. Corneal thickness, visual acuity and blood oxygen levels were measured in climbers before, during and after their ascent, and symptoms of acute mountain sickness were also assessed.
Corneal thickness increased with increasing altitude and decreased after descent, and the amount of decrease in blood oxygen levels paralleled this increase. The group with the shorter acclimatization time experienced a greater increase in corneal thickness. However, no significant decrease in visual acuity was observed in either group.
“It seems that visual acuity in healthy corneas is not adversely affected despite the presence of edema at altitudes up to 6,300 meters,” the authors conclude. Atlanta LASIK surgeon, Dr Farooq Ashraf adds this is not the case in patients who’ve had radial keratotomy. Radial keratotomy is an old refractive procedure in which 4-8 radial incisions are made using surgical blade in order to change the shape of the cornea. “It has been well documented that high altitudes can severely affect vision in these patients and in some cases a few mountain climbers have become functionally blind at these high altitudes,” Dr. Ashraf adds. “LASIK, on the other hand, is unaffected by high altitudes during mountain climbs or even deep sea diving.”
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