Mountain sickness, retinal haemorrhages, and acclimatisation on Mount Everest in 1975.

During the 1975 British Everest Expedition, which made the first ascent of the south-west face, observations were made in relation to mountain sickness and the appearance of retinal changes. Two Sherpas with cerebral oedema and one Briton with pulmonary oedema were treated. Retinal haemorrhages occurred in four out of six Britons who were newcomers to altitudes over 6000 m (19 685 ft) but in only two out of 14 Britons who had previously visited these altitudes. Intraocular pressures during ascent to 6000 m were within normal limits. The relevance of the ocular findings to acclimatisation in previous years was examined, the results supporting the hypothesis of a "carry-over" effect from previous visits to high altitude.