FACT: There is No Negative Affect on High-Altitude Activities After Having LASIK
Elective eye surgery to reduce or eliminate dependence on eyeglasses and contact lenses (“refractive surgery”) has been performed on a large-scale basis since the 1980s. Throughout this time, one of the more popular motivations for people to seek refractive surgery is the ability to perform athletic activities without the encumbrance of spectacle eyeglasses or inconvenience of contact lenses. We have all witnessed sporting events in which an athlete is frantically searching for a lost contact lens while the action plays on around them. It is not surprising, therefore, that amateur and professional athletes have become one of the most enthusiastic groups of refractive surgery patients. Perhaps more than traditional team sport athletes, people whose activities involve extreme environmental conditions have found that refractive surgery can make their endeavors more successful and safer. A prime example is that of high-altitude climbers. These individuals routinely face some of the most stressful environmental conditions, including snow, ice, howling winds and extreme cold. Wearing glasses or contacts in these extreme conditions can not only affect the climber’s performance but also pose serious threats to their safety. Not surprisingly, high altitude climbers and hikers became some of the earliest adapters of refractive surgery.
Radial keratotomy (RK) was the first refractive surgical procedure to gain popularity, starting in the late 1980s. This procedure involved incisions that were specifically designed to weaken the strength of the cornea and, as a result, change the corneal shape in order to reduce nearsightedness. However, in the early 1990s, it was discovered that these effects could be magnified and the individual could end up farsighted – sometimes rather significantly. This phenomenon became well publicized as a result of the tragic events on Mt. Everest in May 1996; one of the climbers had had RK and became severely farsighted while attempting to summit the mountain and suffered significant vision changes. Subsequent research indicated that RK eyes that are exposed to prolonged low oxygen concentrations – such as are encountered in high-altitude climbing – indeed can have significant farsighted changes in their prescription. The structural weakening of the cornea caused by RK was one of the main reasons why this procedure quickly gave way to laser vision correction (LVC) procedures using the excimer laser such as PRK and eventually LASIK in the latter 1990s. Given the disconcerting experience of RK patients who climbed to high altitudes, the natural question was whether similar issues would be observed in LVC patients.
Unlike RK, the corneal shape changes in LVC result from extremely precise removal of microscopic amounts of corneal tissue. Without the significant structural weakening of the cornea, it was assumed that these procedures would not be significantly affected by even extreme altitude changes. Studies have confirmed that indeed high altitudes did not produce corneal shape or prescription changes in eyes that had had PRK to correct nearsightedness. Similar studies in LASIK patients have shown stable corneal shape and prescriptions with one caveat: in some of these patients who had climbed to super-extreme altitudes (above 26,000 feet), mild increase in nearsightedness was observed; this resolved fully during their descent and did not interfere with their ability to function safely.
In conclusion, patients who undergo LVC procedures (PRK or LASIK) for their nearsightedness can safely assume their vision will stay stable even at high altitudes – with the exception of possible mild vision fluctuation at altitudes above 26,000 feet. All told, LASIK should be considered a very safe and effective option for vision correction in high altitude climbers.
Title: Effect of Altitude on LASIK
Authors: Jason W Dimmig MD, Geoff Tabin MD
Précis: The authors report the effects of high altitudes on a group of individuals who had previously had laser in-situ keratomileusis (LASIK) during their multi-day ascent to Mt. Everest (above 26,000 feet). Pre-ascent uncorrected visual acuities were 20/20 in all of the 12 subject eyes at sea level. The patients were then assessed at base camp of 17,600 foot altitude. While visions in all subjects remained unchanged at the 17,600 foot base camp evaluations, 2 of the climbers reported mild visual fluctuation starting at about 26, 400 feet; these resolved by the time they returned to the base camp. Three of the climbers had no reported vision changes even up to the summit at 29,000 feet. The authors noted that these mild vision fluctuations did not interfere with the climbers’ activities. They also observed that this post-LASIK fluctuation in selected subjects at ultra-high altitudes was very different from the uniform hyperopic shift that had been previously reported in post-radial keratotomy (RK) patients who ascended to high altitudes (above 10,00 feet) for prolonged periods. Additionally, the authors noted that individuals who had not had any prior refractive surgery had reported similar vision changes at these ultra-high altitudes and they attributed this to the very extreme hypoxia. The authors concluded that LASIK appeared to be a good and safe refractive surgical option for individuals exposed to high altitudes, certainly superior to RK and probably a better option than spectacles or contact lenses in these scenarios, but those ascending above 26,400 feet should be aware of the possibility of visual fluctuation.
Full reference: Dimmig JW1, Tabin G: The ascent of Mount Everest following laser in situ keratomileusis. J Refract Surg. 2003 Jan-Feb;19(1):48-51
Keywords: LASIK, Laser In-Situ Keratomileusis , Altitude, Hypoxia
Title: Effects of Altitude on Photorefractive Keratectomy
Authors: Col. Thomas H Mader MD, Christopher L Blanton MD, Maj Benjamin N Gilbert MD, Lt. Kenneth C. Kubis MD, LCRD Steven C Schallhorn MD, Lawrence J White MD, LTC Vernon C Parmley MD, Maj John D Ng MD
Précis: The authors present an analysis of several ocular measurements at both sea level and at 14,100 feet in six patients who had undergone prior radial keratotomy (RK), six patients who had undergone photorefractive keratectomy (PRK) and nine myopic patients who had not had any refractive surgery (control group). Measurements included manifest and cycloplegic refractions, keratometry, computerized video keratography and pachymetry. Measurements at 14,100 feet were carried out on three consecutive days. The authors found that the RK patients had a statistically significant increase in spherical equivalent which increased over the three day measurement course (+1.52 + 1.01 diopters on day 3), combined with a decrease in keratometry compared to the control group. The PRK group had no significant change in refractive error or keratometry at the 14, 100 feet altitude. The authors reported that, at the high altitude, pachymetry measurements showed significant peripheral thickening in both surgical groups as well as the control group. All of these changes were observed to be return to baseline after returning to sea level. The authors concluded that 72-hour exposure to high altitude in individuals who have had RK produced significant hyperopic shift in refraction along with keratometric flattening; they attributed this to corneal edema in the area of the RK incisions induced by hypoxia. Importantly, the authors also concluded that excimer laser corneal refractive surgery (PRK in this study) did not induce any significant refractive or keratometric changes at high altitude, thus making this procedure safer than RK for individuals exposed to these altitudes.
Full reference: Mader TH1, Blanton CL, Gilbert BN, Kubis KC, Schallhorn SC, White LJ, Parmley VC, Ng JD: Refractive Changes during 72-hour Exposure to High Altitude after Refractive Surgery. Ophthalmology. 1996 Aug;103(8):1188-95
Keywords: PRK, Photorefractive Keratatectomy, Hypoxia, Altitude
Title: Altitude Effects on Radial Keratotomy
Authors: Lawrence J. White MD, Col. Thomas H. Mader, MC USA
Précis: The authors present a case report of a 40 year old man who underwent uncomplicated radial keratotomy (RK) and had noticed some visual acuity changes when traveling from sea level to 10,000 feet altitudes several months after surgery. The authors tested this by having the patient (then one year after surgery) drive from sea level to 5,000 feet and then 10,000 feet. At each altitude, the authors measured visual acuity, cycloplegic refraction, and keratometry. While the 5,000 feet and sea level measurements were equivalent, measurements at 10,000 feet indicated significant hyperopic shift and corneal flattening. The authors postulated that these changes were induced by hypoxic corneal expansion in the area of the RK incisions resulting in circumferential corneal expansion peripheral to the optical zone and subsequent central flattening. The authors recommended anticipating refractive changes at high altitudes in individuals who have undergone RK.
Full reference: White LJ, Mader TH: Refractive Changes with Increasing Altitude After Radial Keratotomy”. Am J Ophthalmol 1995 Jun, 119(6):733-7
Keywords: RK, Radical Keratotomy, Altitude, Hypoxia