Background/aims The aim of this study was to investigate a change in visual acuity and contrast sensitivity (CS) during high altitude exposure in healthy subjects due to the effects of hypobaric hypoxia. This study is related to the Tübingen High Altitude Ophthalmology study.
Methods Visual acuity and Weber CS were tested monocularly using the Freiburger Visual Acuity and Contrast Test under standardised conditions in 14 healthy subjects at high altitude at the Capanna Margherita (4559 m, Italy) and compared with baseline measurements in Tübingen (341 m, Germany). Intraindividual differences between baseline and follow-up examinations were calculated by multivariate analysis of variance for repeated measures. Clinical parameters of peripheral oxygen saturation (SpO2) and heart rate (HR) as well as scores for acute mountain sickness (AMS) were correlated to psychophysical tests by Pearson’s correlation coefficient.
Results A significant decrease in CS with a mean effect size of −0.13 logCS was found for Weber CS (day 1=−0.16±0.22, p=0.01; day 2=−0.10±0.2, p=0.049; day 3=−0.12±0.19, p=0.03) at high altitude compared with baseline. Visual acuity remained unchanged. Decreased CS correlated with SpO2 (r=0.53, p=0.046) but not with HR (r=− 0.16, p=0.59) and occurred irrespective of AMS at high altitude.
Conclusion High altitude exposure leads to decreased CS. Changes occur independent of AMS. This finding is of clinical importance to trekkers and mountaineers exposed to high altitude as visual processing in particular under mesopic conditions at dusk and dawn is altered. Furthermore, it provides novel insight into hypoxia related changes in CS function.
- contrast sensitivity
- high altitude
- acute mountain sickness
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Contributors KG, AS, KB and GW had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of data analysis. Study concept and design: GW and FG. Acquisition, analysis or interpretation of data: all authors. Drafting of the manuscript: KG and GW. Critical revision of the manuscript for important intellectual content: all authors. Administrative, technical or material support: all authors. Study supervision: GW.
Funding This work was supported by the Wilderness Medical Society with the Charles S. Houston Award.
Disclaimer The supporting source had no role in study design; collection, analysis and interpretation of data; writing the report and the decision to submit the report for publication.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional unpublished data from the study are available.