The effect of hypoxia on intra-ocular, mean arterial, retinal venous and ocular perfusion pressures

Issue title: HYPOXIA

Guest editors: F. Jung and C. Jung

Article type: Research Article

Authors: Baertschi, M.^{a; b; c; *} | Dayhaw-Barker, P.^b | Flammer, J.^a

Affiliations: [a] University of Basel, Department of Ophthalmology, Basel, Switzerland | [b] SALUS University, Philadelphia, PA, USA | [c] Eyeness AG, Hirschengraben, Bern, Switzerland

Correspondence: [*] Corresponding author: Michael Baertschi (PhD), Eyeness AG, Hirschengraben 11, 3011 Bern, Switzerland. Tel.: +41 31 311 07 66; E-mail: [email protected].

Abstract: INTRODUCTION: High altitude hypoxia is linked to decreased blood oxygen saturation with a related increase of Endothelin-1 (ET-1) blood plasma levels. As a consequence of such elevated ET-1 levels, alterations of retinal venous and ocular perfusion pressures are suspected. PURPOSE: To measure the effect of hypoxia on intra-ocular pressure, mean arterial pressure, retinal venous pressure and to calculate ocular perfusion pressure. METHOD: An experimental, prospective cohort study with 33 healthy subjects was conducted in which the subjects were confronted with long-term (days) environmental hypoxia at high altitudes. Mean arterial pressure, arterial blood oxygen saturation, intra-ocular pressure, retinal venous and ocular perfusion pressure were measured at 300 m/1’000 ft (baseline), 4200 m/13’800 ft and 6000 m/19’700 ft above sea level. RESULTS: Arterial oxygen saturation (–13.06% ± 4.69, p = < 0.001; –23.46% ± 5.7,p = < 0.001), retinal venous pressure (+7.16 m Hg±8.2, p = < 0.001;+9.9 mm Hg±8.5, p = < 0.001) and ocular perfusion pressure (–8.49 mm Hg±10.6, p = < 0.001; –6.02 mm hg±11.2, p = 0.006) changed significantly from baseline at both high altitude of 4200 and 6000 m. Intra-ocular pressure did not change significantly at all altitudes (+1.16 mm Hg±4.5, p = 0.227; +0.84 mm Hg±4.8, p = 0.286) and mean arterial pressure changed significantly only at an altitude of 6000 m (+3,8 mm Hg±21.1, p = 0.005) from baseline. CONCLUSION: As hypoxia increases with higher altitude, arterial oxygen saturation and ocular perfusion pressure decreased, retinal venous pressure increased, intra-ocular pressure remains stable and mean arterial pressure was elevated only at 6000 m.

Keywords: Hypoxia, intra-ocular pressure, retinal venous pressure, ocular perfusion pressure, mean arterial pressure, Endothelin, Ophthalmo-Dynamometry, high altitudes, hypobaric

DOI: 10.3233/CH-152025

Journal: Clinical Hemorheology and Microcirculation, vol. 63, no. 3, pp. 293-303, 2016