Fluorescein Angiography during Acute Exposure to High Altitude Reveals Leakage

Abstract

Purpose: : High altitude exposure (HAE) is -due to constantly rising numbers of mountaineers and trekkers- a clinically relevant cause of complex pathophysiological events leading to alterations in all parts of the visual system. Some are well known (e.g. retinal hemorrhages), but the majority of exact mechanisms have not yet been described. The purpose of our study was to evaluate the effects of HAE on retinal blood flow using fluorescein angiography (FA) and assess a correlation to acute mountain sickness (AMS). An increased capillary permeability due to a HIF-1α mediated upregulation of vascular endothelial growth factor (VEGF) has been discussed to be involved in the pathophysiology of AMS.

Methods: : 14 healthy lowlanders ascended from Tübingen (341m, Germany) to the Capanna Margherita (CM; 4554m, Italy) during the Tübingen High Altitude Ophthalmology (THAO) research expedition within 24hours including one overnight stay at 3611m. AMS scores (Lake Louise and AMS-c scores) were assessed twice daily during HAE. Oxygen saturation (SpO2) and heart rate were monitored daily. FA was performed one day after arrival at the CM using Spectralis HRA+OCT (Heidelberg Engineering, Germany). Baseline recordings were taken before and at least 2 weeks after HAE at the University Eye Hospital in Tübingen. No drugs were taken to help the acclimatization process.

Results: : One day after arrival at CM, FA revealed considerable peripheral dye concentrated in the temporal quadrant in 7 out of 14 subjects. Incidence of AMS according to AMS scores was 50% on day2. Only 2 subjects with leakage showed clinically relevant AMS scores. Subjects with AMS had lower SpO2 (71.7±6.54%) and higher heart rate (85.7±9.0/min) compared to those without AMS (74.3±5.48% and 79.8±9.9/min respectively). At baseline FA showed no leakage and all AMS-scores were negative.

Conclusions: : To the best of our knowledge this is the first report of FA revealing leakage during HAE. While incidence for leakage and AMS was found to be 50%, leakage did not correlate with symptoms of AMS. Our data support a hypoxia-induced increased vascular permeability, but do not support its potential role in the pathogenesis of AMS.

Keywords: retina • hypoxia • oxidation/oxidative or free radical damage