As reported in a Researcher Letter, the study included 14 healthy, unacclimatized volunteers (7 male and 7 female participants, average age, 35 years) who were studied at baseline (1,119 feet), after ascent to 14,957 feet within 24 hours, and more than 14 days after return by fluorescein angiography. Photographs were independently graded in random order by 4 ophthalmologists for presence and location of leakage.

Retinal abnormalities were not noted at baseline in any of the participants. At high altitude, marked bilateral leakage of peripheral retinal vessels was observed in 7 of 14 participants (50 percent). All findings completely reversed after descent. "Retinal capillary leakage should be considered a part of the spectrum of high-altitude retinopathy," the authors write.