Influence of hypobaric hypoxic conditions on ocular structure and biological function at high attitudes: a narrative review

Wang, Yuchen; Yu, Xinli; Liu, Ziyuan; Lv, Zhongsheng; Xia, Huaqin; Wang, Yiren; Li, Jiaxi; Li, Xuemin

doi:10.3389/fnins.2023.1149664

Cited by 3 publications

(1 citation statement)

References 43 publications

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“…A large proportion of articles represent case reports [ 7 - 12 ] , while original studies exhibit remarkable inhomogeneity in methodology and instrumentation [ 13 - 16 ] . Likewise, existing reviews have reported a combination of both short- and long-term exposure or the effects of spaceflight on ocular structures [ 17 - 19 ] , or they have focused on a single parameter or effect [ 20 , 21 ] . Meta-analyses, if relevant, are rare and restricted to a single effect [ 22 ] .…”

Section: Introductionmentioning

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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Section: Introductionmentioning

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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Investigating the effects of simulated high altitude on colour discrimination

Liu,

Wang,

et al. 2024

BMJ Open Ophth

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PurposeTo quantify changes in colour vision immediately after exposure to different altitudes of low-pressure hypoxia.MethodsThe study involved 35 healthy participants (ages 20–26). Colour vision was assessed using the Farnsworth-Munsell 100-Hue test at eight different altitudes (condition 1: ground, condition 2: 3500 m, condition 3: 3500 m after 40 min, condition 4: 4000 m, condition 5: 4000 m after 40 min, condition 6: 4500 m, condition 7: 4500 m after 40 min, condition 8: back to the ground). Data were analysed using Analysis of Variance (ANOVA), paired t-test, and χ2test .ResultsTotal Error Score (TES) increased with altitude and hypoxia duration, with higher TES in condition 8 than in condition 1. There were significant TES differences between conditions 3 and 7, as well as 4 and 7. Friedman and repeated ANOVA tests revealed significant sector differences, with Blue-Yellow Partial Error Score (PES) greater than Red-Green PES, particularly on conditions 4, 5 and 8. Significant Red-Green PES differences were found between conditions 4 and 7, and Blue-Yellow PES between conditions 3 and 5, 7, 8. Tritan (Blue-Yellow) shift was most pronounced at high altitudes.ConclusionsThis experiment investigated acute low-pressure hypoxia’s effects on colour vision, supplementing chronic hypoxia research. Increased altitudes and exposure duration worsen colour vision, with effects persisting post-recovery. Tritan axis loss is most significant under hypoxia.

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New insights into changes in ocular structural parameters in a simulated hypobaric hypoxia plateau environment

Wang,

Guo,

et al. 2024

Preprint

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Purpose High altitude is the main area for human exploration, and human eye is an important organ for obtaining visual signals. The changes of eye structure and function caused by hypobaric hypoxia environment need to be clarified. Methods Measurements were taken at five altitudes (1: ground; 2: 3500m; 3: 4000m; 4: 4500m; and 5: end of experiment). Refractive values were measured with the IOL Master (Carl Zeiss Shanghai Co. Ltd.). Data analysis was performed using the Kolmogorov–Smirnov (K-S) test, paired sample T-test, and Wilcoxon test. Results Subjects’ axial length (AL) increased with altitude, peaking at 4500m, then decreased. Significant differences in AL were observed across altitudes (p < 0.05), except between 2 and 5, and 3 and 5. Central corneal thickness (CCT) thickened then thinned with elevation changes, significantly thicker at altitudes 2–5 compared to the baseline (p < 0.05). Lens thickness (LT) followed a similar pattern, increasing up to altitude 4, then decreasing at 5. Correlations were found between AL and LT at altitudes 1 (r = 0.375, p < 0.05) and 5 (r = 0.341, p < 0.05), and between AL and CCT at altitude 4 (r = 0.337, p < 0.05), but not elsewhere. No significant relationship was observed between LT and CCT. Conclusions As altitude increases and the degree of acute low-pressure hypoxia worsens, the refractive parameters such as AL, CCT, and LT are altered, which could potentially affect the pilot's visual function after acute hypoxia, further affecting the pilot's information acquisition and decision-making during driving and posing a threat to flight safety.

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Influence of hypobaric hypoxic conditions on ocular structure and biological function at high attitudes: a narrative review

Cited by 3 publications

References 43 publications

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

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

Investigating the effects of simulated high altitude on colour discrimination

New insights into changes in ocular structural parameters in a simulated hypobaric hypoxia plateau environment

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