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Subfoveal Choroidal Thickness in High-Altitude Mountaineers.

With great interest we have read the study by Fischer et al. on the thickening of the subfoveal choroid in high-altitude mountaineers. They assumed that the reversible choroidal thickening served to counterbalance hypoxia by reactive choroidal hyperperfusion with the goal of maintaining a steady state of oxygen supply to the retinal photoreceptors. In a previous population-based study, thicker subfoveal choroidal thickness was correlated with a higher estimated cerebrospinal fluid pressure. That study had many limitations, including the method to estimate cerebrospinal fluid pressure. However, we would like to ask the authors whether the increase in subfoveal choroidal thickness observed in the mountaineers might have been associated with, or influenced by, an increased cerebrospinal fluid pressure? Although subfoveal choroidal thickness was not associated significantly with indices of acute mountain sickness in the study by Fischer et al., the number of study participants was relatively low to allow a statement on the absence of an association. Also, none of the eight mountaineers had marked acute mountain sickness. Since higher cerebrospinal fluid pressure is associated with higher systemic blood pressure, one also may wonder whether there was an association between blood pressure and subfoveal choroidal thickness in the mountaineers?