Course and Possible Implications of Retinal Hemorrhages at Very High Altitudes

Abstract

Purpose: : Retinal hemorrhages in mountain climbers have been described as a component of high altitude retinopathy (HAR) in association with altitude illness (AI). Retinal bleeding, engorgement and tortuositas of the retinal vessels and optic disc hyperemia develop in many individuals who ascend to heights above 3000m. Possible association of HAR with the potentially fatal high altitude cerebral edema (HACE) has been indicated. We assessed the incidence, time of occurrence of retinal bleeding in a large group of mountaineers at very high altitudes and sought to determine possible correlations with vital parameters.

Methods: : Thirty-two mountaineers were randomly assigned to two different ascent profiles during a medical research expedition to Mt. Muztagh Ata (7546m/ 24,757ft). Digital fundus photographs were taken one month prior to the expedition 400m (1,300ft), at 4497m (14,754ft=base camp), 5533m (18,153ft), 6265m (20,554ft), 6865m (22,523ft), after redescent to base camp (BC2) and 4.5 months thereafter at 400m. Photographs were analyzed by two masked ophthalmologists. Number, size and time of occurrence of hemorrhages were assessed. Vital parameters such as oxygen saturation (SpO2) and acute mountain sickness scores (AMS-c score) were measured at each altitude.

Results: : No hemorrhages could be detected at sea level before and after the expedition. During ascent the amount of retinal bleeding observed increased from 6% of all mountaineers at 4497m to 73% at 6865m. The majority of hemorrhages was detected after descent to base camp, namely in 93% of all climbers. A correlation between SpO2 measurements and total number of hemorrhages was detected (p<0.05, Pearson Correlation Coefficient (PCC)= -0.69). AMS-c scores correlated significantly with total number of hemorrhages at BC2 (p= 0.024, PCC= 0.46).

Conclusions: : There is an increasing incidence of retinal hemorrhages in mountaineers the higher the climb. Interestingly the time of occurrence is belated in relation to ascent. A possible etiology for belated bleeding is reperfusion trauma or a time lag between hypoxic damage to vascular endothelium and leakage of red blood cells. Systemic hypoxia seems to play a significant role in the occurrence of retinal hemorrhages such as in altitude illness.

Keywords: retina • hypoxia • clinical (human) or epidemiologic studies: prevalence/incidence