Exposure to High Altitude May Affect Retinal Vessels

Jennifer Garcia

June 06, 2013

Retinal vessels may leak at high altitudes, even in healthy adults with no previous history of retinal problems, according to a new study published in the June 5 issue of JAMA.

Gabriel Willmann, MD, from the Center for Ophthalmology, University of Tübingen, Germany, and colleagues used fluorescein angiography with a confocal scanning laser to evaluate 14 unacclimatized volunteers at baseline (341 m), after ascent to 4559 m within 24 hours, and more than 14 days after return. Four ophthalmologists blinded to the timing of the photographs graded them for presence and location of leakage.

The researchers found that none of the volunteers demonstrated retinal abnormalities at baseline; however, at high altitude, 50% of participants had marked bilateral peripheral retinal vessel leakage. No leakage was noted in the central retina; all changes reversed after descent.

Acute mountain sickness (AMS) severity was quantified using the Lake Louise and AMS cerebral (AMS-C) scores. The researchers found that leakage was not correlated with AMS or levels of oxygen saturation (SpO2 with leakage, 70.1%; 95% confidence interval [CI], 64.8% - 75.5%; SpO2 without leakage, 74.1%; 95% CI, 68.9% - 79.4%; P = .21). There was also no significant difference in SpO2 between volunteers with or without AMS (71.1% [95% CI, 64.4% - 77.9%] vs 73.1% [95% CI, 69.2% - 77.1%]; P = .54).

The researchers suggest that retinal vessel leakage and subsequent vasogenic edema of surrounding tissue suggests impairment of the blood–retinal barrier. "Whether similar disruptions in the blood-brain barrier cause AMS is unknown, but (taking into account the moderate sample size of this study) the lack of correlation between the retinal findings and AMS does not support this hypothesis," conclude Dr. Willmann and colleagues.

When asked by Medscape Medical News what these findings mean for the average adult traveling to high altitudes, Florian Gekeler, MD, one of the study authors who is also from the Centre for Ophthalmology, University of Tübingen, responded, "Approximately 50% of travelers will suffer from vessel leakage in the retina when exposed to an altitude of 4559 meters or 14,957 ft. Probably this will pass unnoticed, but there is potential relevance for people traveling higher; eg, on a trekking tour to Nepal, or people suffering from retinal disease."

The increasing popularity of mountaineering and commercialization of mountain tours has made AMS a common disorder, notes Javier Ascaso, MD, PhD, from the Department of Ophthalmology of the Lozano Blesa University Clinic Hospital, Zaragosa, Spain, in an email interview with Medscape Medical News. "Nevertheless, the development of high-altitude illness depends not only on the elevation of ascent but also the rate of ascent, the extent that one is acclimatized to high altitude, and the baseline cardiopulmonary status of the individual," noted Dr. Ascaso, who was not associated with the study.

"For patients with diabetes or other diseases where vessels are compromised, the danger of bleedings and edema will probably increase," Dr. Gekeler added. "Most importantly, however, since we have found no correlation to [AMS], the pathogenesis of this disease still remains a mystery."

Researchers agree that retinal vasculature is affected by hypoxia at high altitudes. "The pathophysiology of high-altitude retinopathy remains obscure, but it appears that the physiological limits of the vessels involved are exceeded, and factors other than hypoxia may be involved, such as physical exertion, coughing, and the Valsalva effect," Dr. Ascaso concluded.

Funding for this study was provided by the Charles S. Houston Award from the Wilderness Medical Society. Heidelberg Engineering provided the confocal scanning laser ophthalmoscope. Dr. Gekeler served as a consultant to Retina Implant AG. The other authors and Dr. Ascaso have disclosed no relevant financial relationships.

JAMA. 2013;309:2210-2212. Extract

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....