Chronic hypobaric hypoxia induces a mild degree of pulmonary arterial hypertension with structural alterations in the peripheral portions of the pulmonary arterial tree of the native Andean highlanders. On the other hand, animals indigenous to high altitude do not show these changes and are adapted to hypobaric hypoxia. The small pulmonary arteries of seven native Himalayan highlanders were examined at autopsy and found to be thin-walled with no medial hypertrophy of the muscular pulmonary arteries or muscularization of the arterioles. These findings suggest that the Himalayan highlanders may be adapted to hypobaric hypoxia.

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Abstract. Cardio-pulmonary and physical endurance aspects of high altitude problems have been studied well but not much attention has been paid to the ocular aspects of the problems. 250 cases inducted to a high altitude area in the northern region were examined for ocular parameters within a week of induction and at varying intervals thereafter. Blurred vision was complained of by a number of cases who also suffered from other symptoms of transient mountain sickness. A group of cases who developed acute pulmonary oedema showed fundus changes by way of venous engorgement, papilloedema and superficial retinal haemorrhages. These changes reversed over a period of time as the acute condition subsided. Another group remained asymptomatic b:lt their fundii showed neovascularisation and exudation in addition to retinal haemorrhages. The aetiopathogenesis of these two kinds of changes and other changes is discussed.