Stability of Laser-Assisted In Situ Keratomileusis (LASIK) at Altitude

Aaron, Michelle; Wright, Steve; Gooch, John; Harvey, Rich; Davis, Ryan; Reilly, Charles

doi:10.3357/asem.3325.2012

Cited by 8 publications

(3 citation statements)

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“…For example, previous military studies assessed outcomes of PRK and LASIK under simulated or controlled environments, including firing performance, flight performance, night driving, target detection and identification, as well as aspects associated with adverse or extreme conditions such as low light, high altitude or hypoxia, and G force environment. [1][2][3][11][12][13][14][15][16][17] These studies have yielded positive outcomes and generally supported the operational benefits of PRK and laser in situ keratomileusis. No U.S. military studies to date have performed similar evaluation after the SMILE procedure.…”

Section: Discussionmentioning

confidence: 94%

Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance

Sia

Ryan

Beydoun

et al. 2021

J Cataract Refract Surg

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Section: Discussionmentioning

confidence: 94%

Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance

Sia

Ryan

Beydoun

et al. 2021

J Cataract Refract Surg

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“…After its approval by the USAF in May 2007, over 2200 aircrew underwent LASIK in 2010 [ 54 ] . Studies on LASIK eyes exposed to short-term hyperbaric hypoxia revealed only minor refractive changes, as presented in Table 1 [ 55 - 58 ] .…”

Section: Resultsmentioning

confidence: 99%

“…The same is true for LASIK corneas due to the superficial nature of the surgery [ 59 ] . LASIK eyes, even when exposed to extreme altitudes under military operational conditions (exposure time ≤ 30 min), are expected to remain stable [ 55 ] . In contrast, structural changes in RK corneas result in a hyperopic shift [ 61 - 63 , 141 ] .…”

Section: Discussionmentioning

confidence: 99%

Impact of flight and equivalent short-term high-altitude exposure on ocular structures and function

Totou,

Karmiris,

Kanakis

et al. 2023

Med Hypothesis Discov Innov Ophthalmol

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Background: Exposure to high-altitude conditions during flight or similar activities affects many aspects of visual function, which is critical not only for flight safety but for any altitude-related activity. We aimed to summarize the available literature pertaining to ocular changes during flight or equivalent short-term high-altitude exposure (e.g., hypobaric chamber, effortless ascent lasting less than or equal to 24 h) and to highlight future research priorities. Methods: Using the PubMed/MEDLINE and Web of Science/ISI Web of Knowledge databases with structured search syntax, we conducted a systematic review of the literature spanning a 40-year period (January 1, 1983, to October 10, 2023). Articles pertaining to ocular changes during flight or flight-equivalent exposure to altitude were retrieved. The reference lists of retrieved studies were also searched, and citations of these references were included in the results. Results: Of 875 relevant PubMed and ISI publications, 122 qualified for inclusion and 20 more were retrieved from the reference lists of initially selected records, for a total of 142 articles. Reported anterior segment changes included deterioration in tear film stability and increased dry eye incidence, increased corneal thickness, discomfort and bubble formation in contact lens users, refraction changes in individuals with prior refractive surgery, decreased intraocular pressure, and alterations in pupillary reaction, contrast sensitivity, and visual fields. Photoreceptor–visual pathway changes included alterations in both photoreceptors and neuro-transduction, as evidenced in dark adaptation, macular recovery time, reduction in visual field sensitivity, and optic neuritis (likely an element of decompression sickness). Retinochoroidal changes included increases in retinal vessel caliber, retinal blood flow, and choroidal thickness; central serous chorioretinopathy; and retinal vascular events (non-arteritic ischemic optic neuropathy, high-altitude retinopathy, and retinal vein occlusion). Conclusions: The effect of short-term high-altitude exposure on the eye is, in itself, a difficult area to study. Although serious impairment of visual acuity appears to be rare, ocular changes, including tear film stability, contact lens wear, central corneal thickness, intraocular pressure, contrast sensitivity, stability of refractive surgeries, retinal vessels, visual fields, and macula recovery time, should be considered in civilian aviators. Our report provides guidance to climbers and lowlanders traveling to altitude if they have pre-existing ocular conditions or if they experience visual symptoms while at altitude. However, key outcomes have been contradictory and comprehensive studies are scarce, especially those pertaining to the choroid and retina. Such studies could not only deepen our understanding of high-altitude ocular pathophysiology, but could also offer valuable information and treatment possibilities for a constellation of other vision-threatening diseases.

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Analysis of Impact of Humidity and Temperature on Excimer Laser Ablation of Polyethylene Terephthalate, Polymethylmethacrylate, and Porcine Corneal Tissue

et al. 2019

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Background and ObjectivesTo analyze the impact of humidity and temperature on excimer laser ablation of polyethylene terephthalate (PET), polymethylmethacrylate (PMMA) and porcine corneal tissue, and an ablation model to compensate for the temperature and humidity changes on ablation efficiency.Study Design/Materials and MethodsThe study was conducted using an AMARIS 1050RS (Schwind eye‐tech‐solutions) placed inside a climate chamber at ACTS. Ablations were performed on PET, PMMA, and porcine cornea. The impact of a wide range of temperature (~18°C to ~30°C) and relative humidity (~25% to ~80%) on laser ablation outcomes was tested using nine climate test settings. For porcine eyes, change in defocus was calculated from the difference of post‐ablation to pre‐ablation average keratometry readings. Laser scanning deflectometry was performed to measure refractive change achieved in PMMA. Multiple linear regression was performed using the least square method with predictive factors: temperature, relative humidity, time stamp. Influence of climate settings was modeled for pulse energy, pulse fluence, ablation efficiency on PMMA and porcine cornea tissue.ResultsTemperature changes did not affect laser pulse energy, pulse fluence (PET), and ablation efficiency (on PMMA or porcine corneal tissue) significantly. Changes in relative humidity were critical and significantly affected laser pulse energy, high fluence and low fluence. The opposite trend was observed between the ablation performance on PMMA and porcine cornea.ConclusionsThe proposed well‐fitting multi‐linear model can be utilized for compensation of temperature and humidity changes on ablation efficiency. Based on this model, a working window for optimum operation has been found (temperature 18°C to 28°C and relative humidity 25% to 65%) for a maximum deviation of ±2.5% in ablation efficiency in PMMA and porcine corneal tissue. Lasers Surg. Med. © 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

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Stability of Laser-Assisted In Situ Keratomileusis (LASIK) at Altitude

Abstract: LASIK eyes exposed to extreme altitudes under operational conditions, where the exposure is limited to 30 min or less, are expected to remain stable.

Cited by 8 publications

References 0 publications

Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance

Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance

Impact of flight and equivalent short-term high-altitude exposure on ocular structures and function

Analysis of Impact of Humidity and Temperature on Excimer Laser Ablation of Polyethylene Terephthalate, Polymethylmethacrylate, and Porcine Corneal Tissue

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