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P. K. Kofoed, B. Sander, G. Zubieta-Calleja, Jr., K. Klemp, M. Larsen; Effect of High to Low Altitude Adaptation on the Multifocal Electroretinogram. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5379.
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Oxygen supply is fundamental for retinal function. Hypoxia and ischemia are considered essential elements of the pathogenesis of many eye diseases. We investigated the impact of habitual low ambient oxygen tension and chronic adaptation to higher oxygen tensions by examination of high altitude residents immediately after descent to sea level and during 2½ month stay at sea level. Retinal neuronal adaptation was studied using multifocal electroretinography. Assessment of systemic circulatory parameters included blood pressure, hematocrit, hemoglobin, and erythropoietin.
A group of eight habitual highlanders (altitude 3600 m) were examined during adaptation from hypobaric atmospheric conditions to normobaric normoxia over a period of 74 days. The study included a control group of eight age- and sex-matched sea level residents.
Electroretinography demonstrated significant higher amplitudes (N1, P1, N2) in highlanders than in sea level controls. During the adaptation process all three peaks increased significantly in amplitude, from baseline to day 73 (p<0.001). Hemoglobin concentration decreased (p=0.0033), erythrocytes decreased (p<0.001), hematocrit decreased (p<0.001), and erythropoietin increased (p=0.0137) during the study. Significant correlation was found between electrophysiological and hematological changes.
This is the first report of long term adaptive electrophysiological changes during acclimatization to sea level altitude after translocation from life-long living at high altitude under permanent hypobaric hypoxia. We documented correlations between the increased electroretinographic amplitudes and the fall in red blood cell concentration during adaptation. This correlation suggests that the relation between physiological variables is complex, especially because the abnormally high electroretinographic amplitude seen immediately after transition to sea level continues to grow during the 2½ months long stay at sea level. Our results suggest that recent changes in altitude of residence may significantly affect ERG amplitudes, a finding that may need to be taken into consideration in clinical or academic ERG studies.
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