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By Todd Neale, Senior Staff Writer, MedPage Today Reviewed by Zalman S. Agus, MD; Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse PlannerAt high altitude, marked bilateral leakage of peripheral retinal vessels was observed in half of the participants in this small study which completely reversed after descent.The peripheral leakage was not correlated with acute mountain sickness.Leakage of the retinal vessels is common at high altitudes, although it doesn't appear to be a major contributing cause of acute mountain sickness, researchers found.
Half of healthy volunteers who ascended to nearly 15,000 feet had "marked bilateral leakage of peripheral retinal vessels" confined to the temporal-inferior periphery, according to Florian Gekeler, MD, of the University of Tübingen in Germany, and colleagues.
All evidence of leakage disappeared when the participants returned to a baseline elevation of 1,119 feet, the investigators reported in a research letter in the Journal of the American Medical Association.
"To our knowledge, this finding in the most distal vascular bed of the retina (where tissue hypoxia is most severe) has not been detected in previous studies," they wrote. "Retinal capillary leakage should be considered a part of the spectrum of high-altitude retinopathy."
However, the leakage is unlikely to be a primary cause of acute mountain sickness -- as has been hypothesized -- because the retinal findings were not associated with either scale used to define the condition in the study.
The researchers examined retinal vessel integrity at high altitudes among 14 healthy volunteers (mean age 35; 50% female) using fluorescein angiography with a confocal scanning laser ophthalmoscope.
Retinal examinations were performed at the baseline elevation, again after the participants ascended to an elevation of 14,957 feet within 24 hours, and finally more than 14 days after returning to baseline.
The severity of acute mountain sickness was assessed using the Lake Louise and AMS cerebral (AMS-C) scores, which included both self-reported and objective measurements.
None of the participants had retinal abnormalities at baseline, but 50% developed leakage of the peripheral vessels at high altitude.
Half of the participants also met criteria for acute mountain sickness, although the condition was not associated with retinal vessel leakage. Leakage was seen in 43% of those with and 57% of those without acute mountain sickness.
Leakage also was not associated with peak peripheral oxygen saturation measured by pulse oximeter; the peak saturation was 70.1% in those with and 74.1% in those without leakage (P=0.21).
Only one participant had a retinal hemorrhage, which was not associated with vessel leakage.
The researchers noted that "a comparable hemispherical presentation [of retinal vessel leakage] occurs in zone III of retinopathy of prematurity. Leakage of retinal vessels with vasogenic edema of surrounding tissue suggests impairment in the tight junctions of the retinal capillary endothelial cells, the blood-retinal barrier."
"Whether similar disruptions in the blood-brain barrier cause acute mountain sickness is unknown, but (taking into account the moderate sample size of this study) the lack of correlation between the retinal findings and [the condition] does not support this hypothesis," they wrote.
The study was supported by the Charles S. Houston Award from the Wilderness Medical Society. Heidelberg Engineering provided the confocal scanning laser ophthalmoscope.
Gekeler reported serving as a consultant to Retina Implant AG.
Primary source: Journal of the American Medical Association
Source reference:
Willmann G, et al "Retinal vessel leakage at high altitude" JAMA 2013; 309: 2210-2212.
Todd Neale
Senior Staff Writer
Todd Neale, MedPage Today Staff Writer, got his start in journalism at Audubon Magazine and made a stop in directory publishing before landing at MedPage Today. He received a B.S. in biology from the University of Massachusetts Amherst and an M.A. in journalism from the Science, Health, and Environmental Reporting program at New York University.
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