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Francisco J. Ascaso, Isabel Pinilla, María A. Nerín, Laura Villén, José R. Morandeira, María A. Del Buey, José A. Cristóbal; Acute Mountain Sickness and Retinal Nerve Fiber Layer Evaluation using Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3668.
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© ARVO (1962-2015); The Authors (2016-present)
Acute mountain sickness (AMS), the most common form of altitude illness, might represent early-stage high altitude cerebral edema (HACE). It is well known that the development of AMS symptoms is correlated with a higher increase in retinal capillary blood flow and with optic disc swelling. The aims of this study were to measure the peripapillary retinal neve fiber layer (RNFL) thickness and optic nerve head (ONH) parameters following a sojourn to extreme altitude.
This prospective study included three high-altitude expeditions in the Himalayan region. Twelve eyes of 6 healthy male, well trained, experienced climbers underwent baseline and post-expedition complete ophthalmic examination, including optical coherence tomography (OCT) to measure peripapillary RNFL thickness, ONH parameters, and macular thickness and volume. Lake Louise AMS Scoring System (LLS) self-report questionnaire was used to estimate AMS severity.
All mountaineers experienced symptoms of mild AMS (LLS: 4.8±0.9, range: 4.0-6.0). Unlike average RNFL thickness, superior, inferior and nasal quadrants thickness, only the temporal quadrant of peripapillary RNFL showed a significant increased thickness in post-expedition examination (74±17 µm, range: 48-100), compared with baseline values (64±12 µm, range: 42-83) (p=0.008, Wilcoxon signed-rank test). With respect to ONH analysis results, vertical integrated rim area was significantly higher in post-expedition examination (0.65±0.39 mm3, range: 0.14-1.49) than that in baseline examination (0.51±0.26 mm3, range: 0.10-1.00) (p=0.012, Wilcoxon signed-rank test). Likewise, horizontal integrated rim area was significantly higher in post-expedition examination (1.90±0.33 mm2, range: 1.37-2.33) than that in baseline examination (1.78±0.26 mm2, range: 1.28-2.08) (p=0.012, Wilcoxon signed-rank test). The remaining ONH and macular measurements did not show significant differences between baseline and post-expedition examinations. There was no correlation between LLS and OCT parameters (p>0.05, Spearman's correlation coeficient).
In climbers suffering from AMS, OCT was able to detect subtle increases in the peripapillary RNFL thickness and in some ONH measurements, even in absence of HACE and papilledema. These changes might be a sensitive parameter in physiological acclimatization and in the pathogenesis of AMS.
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