The effect of high- to low-altitude adaptation on the multifocal electroretinogram

Peter Kristian Kofoed, Birgit Sander, Gustavo Zubieta-Calleja, Line Kessel, Kristian Klemp, Michael Larsen, Peter Kristian Kofoed, Birgit Sander, Gustavo Zubieta-Calleja, Line Kessel, Kristian Klemp, Michael Larsen

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    Abstract

    PURPOSE: To examine variations in retinal electrophysiology assessed by multifocal electroretinogram (mfERG) during acclimatization of native highlanders to normobaric normoxia at sea level. METHODS: Eight healthy residents of the greater La Paz area in Bolivia (3600 m above sea level) were examined over 72 days after arriving in Copenhagen, Denmark (sea level). A control group of eight healthy lowlanders was used for comparison. RESULTS: During the period of observation, hemoglobin decreased from 16.7 to 15.0 g/dL (P = 0.0031), erythrocytes decreased from 5.3 to 4.6 trillion cells/L (P = 0.0006), and hematocrit decreased from 49.4% to 42.2% (P = 0.0008). At baseline, day 2 after arrival, the amplitudes (N1, P1, and N2) of the mfERG were 43.1% to 59.9% higher in the highlanders than in the lowlanders (P < 0.017). During acclimatization, the mfERG amplitudes increased 16.9% to 20.4% (P < 0.028) to a level of 73.2% to 87.0% higher in the highlanders than in the lowlanders (P < 0.0008). The increase in numerical amplitudes was proportional to the decrease in erythrocyte concentration (P = 0.023, 0.053, and 0.12 for N1, P1, and N2, respectively). CONCLUSIONS: On arrival at sea level, the highlanders had markedly supernormal multifocal electroretinographic amplitudes that continued to increase during the 72-day period of observation where the highlanders' hematocrit normalized. The results suggest that acclimatization after a change in altitude and hence in ambient oxygen tension involves intrinsic retinal mechanisms and that acclimatization was not complete by the end of the study.
    Original languageEnglish
    JournalInvestigative Ophthalmology & Visual Science
    Volume50
    Issue number8
    Pages (from-to)3964-9
    Number of pages6
    ISSN0146-0404
    DOIs
    Publication statusPublished - 1 Aug 2009

    Bibliographical note

    Keywords: Acclimatization; Adult; Altitude; Blood Glucose; Electroretinography; Erythrocyte Count; Female; Hematocrit; Hemoglobins; Humans; Intraocular Pressure; Male; Oxygen; Oxygen Consumption; Retina

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