Radial Keratotomy (RK) — An Older, Non-Laser Vision Correction Technique — Has Been Associated With Visual Problems at Extreme Altitudes. LASIK and PRK Laser Vision Correction, However, Appear to Perform Well at Extremely High Altitude. Mountaineers and other patients interested in mountain sports such as skiing or backpacking have asked me about the effects of high altitude on LASIK laser vision correction eye surgery. This is a particularly important issue since glasses and contact lenses might not perform well under these conditions.
Concern about the performance of LASIK at high elevations stems from problems noted with an earlier non-laser refractive surgery proceedure that is no longer performed — radial keratotomy (RK). With radial kertatotomy (but not with LASIK or PRK), researchers have noticed that the eye becomes more farsighted at very high altitudes. Much of the concern about this older technique of radial keratotomy is based on a incident in the book Into Thin Air, which describes a terrible expedition on Mount Everest in which 8 climbers lost their lives. One of the fellow climbers in this tragic story, Dr. Beck Weathers, previously had undergone radial keratotomy. Dr. Weathers did manage to survive and get off the mountain, but he famously developed farsightedness (hyperopic shift) with radial keratotomy at very high altitude (approximately 26,000 feet above sea level). The blurry vision was significant enough for him to abandon his attempt to reach the summit after leaving Everest’s Camp Four. The visual problems resolved when Dr. Weathers returned to lower altitude. Most researchers feel that Dr. Weathers’ visual problems were related to oxygen deprivation at this extreme altitude and the interaction of that oxygen deprivation with the incisions created by RK (incisions not made in laser vision correction).
Another report in the medical literature discusses 2 expert climbers who previously had radial keratotomy surgery. They developed farsighted shifts and blurry vision at altitudes above 16,400 feet on Mount McKinley and Mount Everest. Again, the culprit appears to be the effects of oxygen deprivation on the RK incisions.
Other reports, on the other hand, have not shown farsighted changes in eyes with radial keratotomy at 12,000 feet or even higher, which are elevations we might encounter in the Sierra Nevada Range here in California. In general, while there is debate and while later forms of radial keratotomy may not have had this type of problem to this degree, many ophthalmologists caution patients who previously had radial keratotomy that their vision might become more farsighted and therefore blurry at altitude above 9,000 feet, which is an altitude we easily could spend time at even in Mammoth going skiing. At altitudes we would encounter in California, though, a simple pair of “cheaters” likely would solve the visual problem for patients with radial keratotomy since the altitudes we experience here are not as extreme as the 26,000 feet Dr. Weathers was exposed to on Mount Everest.
By contrast, there is very strong evidence that laser vision correction should be the procedure of choice for patients who will be exposed to extremely high altitudes — either LASIK or PRK (which should not be confused with RK or “radial keratotomy”). Laser vision correction does not cause the type of farsighted changes at extreme altitude that were seen with radial keratotomy.
Studies have looked at the performance of LASIK at very high altitude. A 2003 study looked at 6 Mount Everest climbers who all had undergone LASIK. 3 of these climbers noticed no problems and perfect vision at the summit (29,029 feet above sea level). 1 reported mild blurring above 16,000 feet that improved either with a prolonged stay at high altitude or with coming down.. 2 climbers reported blurred vision at 27,000 feet and 28,500 feet respectively which improved with descent. This study leads some experts to say that LASIK will overall perform very well at extremely high altitudes — higher than we have anywhere in California — but that above 26,000 feet patients should be aware of possible fluctuations. The cause of these fluctuations is not clear. Some researchers feel there may be a very mild shift toward more nearsightedness at extreme altitude and others postulate the shifts are just due to dry eye, which is common in the extreme conditions and low humidity at such high altitudes.
Another study involved an ophthalmologist who climbed with his wife (who had previously undergone LASIK) to 18,500 feet and demonstrated no change in her vision at this extreme altitude — an altitude higher than any point in California.
The performance of laser eye surgery at perhaps the most extreme altitude of all, however, was recently scientifically measured. In a study published this month in the Journal of Cataract and Refractive Surgery, the performance of PRK laser eye surgery was studied during spaceflight on the International Space Station. I’ll discuss this fascinating — and reassuring — study in my next blog.
See Also
Refractive Changes at High Altitude After LASIK
Going to High Altitude with Preexisting Ocular Conditions
Effect of High Altitude Exposure on Myopic Laser In Situ Keratomileusis
Ophthalmological Effects of High Altitude
The Ascent of Mount Everest Following Laser In Situe Keratomileusis (LASIK)
Refractive Changes in Response to Acute Hyperbaric Stress in Refractive Surgery Patients
Lonely Planet Thread on Travelers with Laser Eye Surgery At High Altitude