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

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 (+ 7.16m Hg+/-8.2, p = < 0.001;+ 9.9mm Hg+/-8.5, p = < 0.001) and ocular perfusion pressure (-8.49mm Hg+/-10.6, p = < 0.001; -6.02mm 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 (+ 1.16mm Hg+/-4.5, p = 0.227; + 0.84mm Hg+/-4.8, p = 0.286) and mean arterial pressure changed significantly only at an altitude of 6000m (+ 3,8mm 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.