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M. M. Bosch, D. Barthelmes, T. M. Merz, F. K. P. Sutter, K. E. Bloch, A. J. Turk, U. Hefti, M. G. Wirth, M. Maggiorini, K. Landau; Optic Disc Swelling at High Altitudes Varies With Age. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2473.
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To determine and analyze the incidence of optic disc swelling in healthy mountaineers of various ages at different altitudes during an expedition to very high altitudes.
Thirty-two mountaineers took part in a medical research expedition to Muztagh Ata (7546m/24,757ft), Western China. Fundus photographs were taken one month prior to the expedition at 400m (1,300ft), 4497m (14,754ft), 5533m (18,153ft), 6265m (20,554ft), 6865m (22,523ft) and 4 months thereafter at 400m. The optic discs were graded by three masked ophthalmologists in three groups (0= no swelling, 1= possible swelling, 2= swollen disc). Acute mountain sickness-cerebral (AMS-c) scores of the environmental symptoms questionnaire and oxygen saturation were assessed on every expedition day. Statistical significance was defined as p < 0.05.
Complete data records of 27 participants (54 eyes) were analyzed. 16 of 27 mountaineers (60%) were observed to have bilateral swollen discs (8 climbers) or a unilateral swollen disc and possible swelling of the contralateral disc (n=8). Logistic regression revealed significant positive correlation of optic disc swelling with AMS-c score (r=0.229, p=0.033) and negative correlation with age (r=-0.232, p=0.003) and oxygen saturation (r=-0.27, p=0.012).
Optic disc swelling has a high incidence in mountaineers climbing to high altitudes. Positive correlations with AMS score and low oxygen saturation suggest optic nerve swelling as a marker of subclinical high altitude cerebral edema.The observed protective effect of age on optic disc swelling may be explained by the increasing ratio of cranial cerebrospinal fluid to brain volume.
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