Purpose

Acute mountain sickness (AMS), the commonest form of altitude illness, might represent early-stage high altitude cerebral edema (HACE). Optical coherence tomography (OCT) was used to evaluate optic nerve head (ONH) consequences following a sojourn to extreme altitude.

Methods

This prospective study included 4 high-altitude expeditions in Himalayas. Twenty-four eyes of 12 healthy male climbers underwent baseline and postexpedition complete ophthalmic evaluation, including OCT to measure the peripapillary retinal nerve fiber layer (RNFL) thickness, ONH parameters, and macular thickness and volume. Lake Louise Scoring (LLS) self-report questionnaire was used to estimate AMS severity.

Results

All mountaineers experienced symptoms of AMS (LLS: 5.1±1.1, range 4.0-7.0). Average peripapillary RNFL thickness showed a significant increase in postexpedition examination (94±23 μm, 47-115), compared with baseline values (89±19 μm, range 45-114) (p=0.034). Superior (p=0.036) and temporal (p=0.010) quadrants also showed an increased RNFL thickness following exposure to high altitude. Vertical integrated rim area (VIRA) was significantly higher in postexpedition examination (0.71±0.43 mm³, 0.14-1.50) than in baseline examination (0.51±0.26 mm³, 0.11-1.00) (p=0.002). Horizontal integrated rim width was significantly higher in postexpedition examination (1.90±0.32 mm², range 1.37-2.34) than in baseline examination (1.77±0.27 mm², 1.27-2.08) (p=0.004). There was no correlation between LLS and OCT parameters (p>0.05).

Conclusions

In climbers with AMS, OCT was able to detect subtle increases in the peripapillary RNFL thickness and in some ONH measurements, even in absence of HACE and papilledema. These changes might be a sensitive parameter in physiologic acclimatization and in the pathogenesis of AMS.