Impact of Acute Exposure to High Altitude on Anterior Chamber Geometry

Abstract

Purpose: This study aimed to quantify the impact of acute exposure to high altitude on central corneal thickness and the geometry of the anterior chamber angle. This work is related to the Tuebingen High Altitude Ophthalmology (THAO) study.

Methods: Anterior segment spectral domain optical coherence tomography was used to quantify changes of central corneal thickness, anterior chamber angle and angle opening distance in 14 healthy subjects between baseline recordings (341 m) and during acute exposure to high altitude (4559 m).

Results: Detailed longitudinal analysis revealed highly significant (p < 0.0001) increased central corneal thickness (CCT) in healthy subjects during acute altitude exposure (CCTbaseline = 517.53±28.28 μm vs. CCTaltitude = 539.87±31.28 μm; mean±sd). This change was completely reversible upon descend and no subject demonstrated persisting structural or functional sequels. Geometric measures of the anterior chamber angle remained consistent with no significant changes in angle opening distance (AOD) at 500 μm (AODbaseline = 695.96±190.00 μm vs. AODaltitude = 673.71±179.59 μm; p = 0.52) and stable measurements of anterior chamber angle (ACA) in degree (ACAbaseline = 37.85±6.53 vs. ACAaltitude = 36.29±5.81 μm; p = 0.34).

Conclusions: Significant changes of CCT occur in response to acute exposure to high altitude in healthy control subjects. This might be due to decreased atmospheric pressure and consequently decreased blood oxygen saturation (SpO2) in non-acclimatized subjects and constitute a mild corneal edema formation. Interestingly, AOD at 500 μm and ACA remained stable during the acute challenge to hypoxic conditions at high altitude. This is the first time a quantitative approach has been used to assess changes of the anterior segment during acute, non-acclimatized high altitude exposure. As such, it might provide a basis for the debate on changes of intraocular pressure during exposure to high altitude.

Keywords: 548 hypoxia • 421 anterior segment • 420 anterior chamber