Dear Sir,
We greatly appreciate the interest and the response to our article that described a young healthy man who developed multiple intraretinal hemorrhage bilaterally and macular hemorrhage in the left eye due to high-altitude retinopathy.[1,2] Spectral-domain optical coherence tomography detected a thickening of the choroidal layer bilaterally with the choroidal thicknesses at the fovea of 530 mm OD and 490 mm OS. These are thicker than that in normal subjects of approximate 300 mm.
High-altitude retinopathy is relatively benign, and the hemorrhage usually resolves spontaneously. However, the development of high-altitude retinopathy is the first sign of high-altitude cerebral edema which can progress to death.[3] The increase of retinal blood flow in mountaineers with retinal hemorrhages and dilated epipapillary network has been detected with the Heidelberg retina flowmeter after acute hypoxic stress at high-altitude.[4] The increase of retinal blood blow and cerebral blood flow under hypoxic conditions may also be associated with the increase of choroidal blood flow resulting in an increase of choroidal thickness.[1,2]
Tan et al. reported large topographic variations of the choroidal thickness in the central and other sectors of the Early Treatment Diabetic Retinopathy Study grid of 124 healthy Chinese adults.[5] The mean central subfield choroidal thickness of these individuals was 322.2 mm that is comparable to the values for normal eyes in the literature. Our patient was emmetropic with refractive errors of −0.25 diopters OD and −0.50 diopters OS, which were not high mopic. However, the choroidal thickness was measured only once, and it is known that there is a diurnal variation in the choroidal thickness.[6]
As we described, it is difficult to draw strong conclusions from a single case and the measurement at only one-time point. We also hope that our findings will stimulate further studies evaluating the choroidal thickness in mountaineers with acute mountain sickness to determine whether measurements of the choroidal thickness may be useful in evaluating and predicting high-altitude cerebral edema.
Again, we thank the authors for their interest.
References
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