Multifocal electroretinography changes in the macula at high altitude: a report of three cases

To evaluate the short- and long-term effects of high-altitude hypobaric hypoxia on macula morphology and function during ascents, acclimatizations, and descents between 500 m and 5,650 m, macula function was evaluated in three healthy climbers of a trekking expedition.

Macula physiology was tested with multifocal electroretinography (MF ERG), near and farvisual acuity, and Amsler grid tests. Macula morphology was tested with optical coherence tomography (OCT) and with stereoscopic fundoscopy obtained 1 week before ascent, as well as 1 week and 2 weeks after high-altitude exposure. The following physiological parameters indicative of acclimatization were compared daily during the expedition at altitudes between 500 m and 5,050 m: hemoglobin, oxygen saturation, resting heart rate, retinal findings, and the Lake Louise score of acclimatization.

The central macula MF ERG responses were significantly reduced 1 week after high-altitude exposure, and had recovered by the follow-up examination performed during the following week. Near visual acuity and Amsler grid tests remained unaffected at both follow-up examinations. No significant changes were found in the follow-up OCT and daily fundoscopy examinations in all three well-acclimatized climbers.

High-altitude hypobaric hypoxia affects the function of the highly sensitive macula region. This suggests that the exposure of persons with macula diseases such as age-related macula degeneration, tapetoretinal degeneration, or diabetic retinopathy to high altitudes may influence the disease progression. For this reason, this population should avoid prolonged and unnecessary high-altitude exposure without proper acclimatization.