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Karel Van Keer, Joao Barbosa-Breda, Raf De Jongh, Ivo Nijs, Mieke Wirix, Luís Abegão Pinto, Ingeborg Stalmans, Evelien Vandewalle; The eye at high altitude.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3951.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the physiological response and recovery of retro-bulbar, choroidal and retinal circulations to exposure to simulated high-altitude in healthy individuals.
Participants were examined with Optical Coherence Tomography (OCT), angio-OCT, retinography and colour Doppler imaging before, during and after a six-hour exposure to a simulated height of 4000m in a normobaric hypoxic chamber. Retinal nerve fiber layer (RNFL) and choroidal (CT) thicknesses were measured on structural OCT-scans. Vessel density in the macular and peripapillary areas were quantified as the mean gray value on angio-OCT images using ImageJ®. Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were measured on retinographies using iFlexis® software. Repeated measures ANOVA was used to assess the changes within patients over time.
Eighteen eyes of 18 healthy individuals aged 34.5±16.4 years were analyzed. RNFL, CT, peripapillary vessel density and CRVE showed a significant increase after six hours of hypoxia exposure (p = 0.036, p < 0.001, p = 0.040 and p <0.001 respectively) that was accompanied by a decrease in resistive and pulsatility indexes (both p<0.001) and an increase in ophthalmic artery flow velocities (p < 0.001). After one hour of recovery at sea level conditions, all the changes returned to baseline values.
We demonstrated that in healthy individuals a decrease in ambient oxygen saturation is compensated at the retrobulbar, choroidal and retinal micro- and macro-circulatory level. These changes quickly recover back to baseline upon return to normoxic conditions .
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Relative changes in central retinal venular equivalent, choroidal thickness, peripapillary vessel density, retinal nerve fiber layer thickness and ophthalmic artery resistive index at baseline, after a six-hour exposure to a simulated height of 4000m and one hour after removal of the hypoxic stimulus
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