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.
ArjamaaO. and NikinmaaM., Oxygen-dependent diseases in the retina: Role of hypoxia-inducible factors, Exp Eye Res83(3) (2006), 473–483.
2.
BaertschiM., Factors influencing Retinal Venous Pressure, in Graduate Program of Biomedicine. 2015, SALUS University, 204.
3.
BoschM.M., et al., High incidence of optic disc swelling at very high altitudes, Arch Ophthalmol126(5) (2008), 644–650.
4.
BoschM.M., et al., Intraocular pressure during a very high altitude climb, Invest Ophthalmol Vis Sci51(3) (2010), 1609–1613.
5.
BoschM.M., et al., New insights into changes in corneal thickness in healthy mountaineers during a very-high-altitude climb to Mount Muztagh Ata, Arch Ophthalmol128(2) (2009), 184–189.
6.
BoschM.M., et al., New insights into ocular blood flow at very high altitudes, J Appl Physiol106(2) (2009), 454–460.
7.
BraunU., BraunM. and JonasJ.B., [High altitude retinopathy after Himalayan ascent], Klin Monbl Augenheilkd211(3) (1997), 213–214.
8.
ButlerF.K., HarrisD.J.Jr and ReynoldsR.D., Altitude retinopathy on Mount Everest, Ophthalmology99(5) (1992), 739–746.
9.
CelliniM., et al., Endothelin-1 plasma levels and vascular endothelial dysfunction in primary open angle glaucoma, Life Sci91(13-14) (2012), 699–702.
10.
ChenY.F. and OparilS., Endothelin and pulmonary hypertension, J Cardiovasc Pharmacol35(4 Suppl 2) (2000), S49–S53.
11.
ErgulA., Endothelin-1 and diabetic complications: Focus on the vasculature, Pharmacol Res63(6) (2011), 477–482.
12.
ErshlerP. and ErshlerS., Together on top of the world: The remarkable story of the first couple to climb the faibled seven summits. 2007, New York: Warner Books, Hachette Book Group. pp. 365.
13.
FlammerJ. and MozaffariehM., Autoregulation: A balancing act between supply and demand, Can J Ophthalmol43(3) (2008), 317–321.
14.
GoerreS., et al., Endothelin-1 in pulmonary hypertension associated with high-altitude exposure, Circulation91(2) (1995), 359–364.
15.
HonigmanB., et al., High altitude retinal hemorrhages in a Colorado skier, High Alt Med Biol2(4) (2001), 539–544.
16.
IannacconeA., et al., Plasma endothelin-1 concentrations in patients with retinal vein occlusions, Br J Ophthalmol82(5) (1998), 498–503.
17.
KaiserH.J., et al., Endothelin-1 plasma levels in normal-tension glaucoma: Abnormal response to postural changes, Graefes Arch Clin Exp Ophthalmol233(8) (1995), 484–488.
18.
KanazawaF., et al., Expression of endothelin-1 in the brain and lung of rats exposed to permanent hypobaric hypoxia, Brain Res1036(1-2) (2005), 145–154.
19.
KangJ., et al., Chronic intermittent hypoxia versus continuous hypoxia: Same effects on hemorheology?Clin Hemorheol Microcirc, 2015, Sep 25 (epub ahead of print).
20.
KikstraH., Report: What happened to Thomas Lincoln and Harry. SightonEverest.com Everest 2006 Internet, 2006(May): pp. 8.
21.
KonieczkaK., et al., Refractoriness to the effect of endothelin-1 in porcine ciliary arteries, J Ocul Pharmacol Ther29(5) (2013), 488–492.
22.
KoutsiarisA.G., Correlation of axial blood velocity to venular and arteriolar diameter in the human eye in vivo, Clin Hemorheol Microcirc (2014).
23.
KurvinenL., et al., Altered temporal peripapillary retinal flow in patients with disc hemorrhages, Graefes Arch Clin Exp Ophthalmol248(12) (2010), 1771–1775.
24.
LamH.C., et al., Role of endothelin in diabetic retinopathy, Curr Vasc Pharmacol1(3) (2003), 243–250.
25.
LeeA.G., AldamaA.E. and HarperR.L., High altitude retinopathy, J Neuroophthalmol19(3) (1999), 205–206.
26.
LeeN.Y., et al., Analysis of systemic endothelin-1: Matrix metalloproteinase-9, macrophage chemoattactarnt protein-1, and high-sensitivity C-reactive protein in normal-tension glaucoma, Curr Eye Res37(12) (2012), 1121–1126.
27.
LichtenauerM., et al., Simulated temporary hypoxia triggers the release of CD31+/Annexin+endothelial microparticles: A prospective pilot study in humans, Clin Hemorheol Microcirc, 61(1) (2015), 83–90.
28.
ModestiP.A., et al., Role of endothelin-1 in exposure to high altitude: Acute Mountain Sickness and Endothelin-1 (ACME-1) study, Circulation114(13) (2006), 1410–1416.
29.
MorgantiA., et al., Effects of exposure to high altitude on plasma endothelin-1 levels in normal subjects, J Hypertens13(8) (1995), 859–865.
30.
MorgantiA., et al., Plasma endothelin levels: A meaningless number?S, J Cardiovasc Pharmacol35(4 Suppl 2) (2000), 21–23.
31.
MozaffariehM., et al., Retinal venous pressure in the non-affected eye of patients with retinal vein occlusions, Graefes Arch Clin Exp Ophthalmol (2014).
32.
MozaffariehM. and FlammerJ., Pocket Reference to Ocular Blood Flow and Glaucomatous Optic Neuropathy. 2008, London: Current medicine Group. 105.
33.
Mullner-EidenbockA., et al., High-altitude retinopathy and retinal vascular dysregulation, Eye (Lond)14(5) (2000), 724–9.
34.
PavlidisM., et al., Intraocular pressure changes during high-altitude acclimatization, Graefes Arch Clin Exp Ophthalmol244(3) (2006), 298–304.
35.
RuizM., Everest Climber dies after reaching summit. aolnews.com, 2010(June): pp. 2.
36.
ShultsW.T. and SwanK.C., High altitude retinopathy in mountain climbers, Arch Ophthalmol93(6) (1975), 404–408.
37.
StodtmeisterR., et al., Contact lens dynamometry: The influence of age, Invest Ophthalmol Vis Sci51(12) (2010), 6620–6624.
38.
StodtmeisterR., et al., Enhanced pressure in the central retinal vein decreases the perfusion pressure in the prelaminar region of the optic nerve head, Invest Ophthalmol Vis Sci54(7) (2013), 4698–4704.
39.
WangL., et al., Lower Limit of Blood Flow Autoregulation in Optic Nerve Head, in ARVO, InstituteDE., Editor. 2012: Ft. Lauderdale. pp. D1181.
