We thank Dr Abdullah Kaya for his valuable comments on our article. We reported the thickened subfoveal choroid in eyes with choroidal melanoma that are not localized in the macular area. This finding may illustrate that a localized choroidal melanoma has diffuse choroidal involvement. We hypothesized that the increase in subfoveal choroidal thickness was due to an increase in choroidal blood flow to account for the increased metabolic activities in tumorigenesis, since metabolically active tumors defined by positron emission tomography–computed tomography showed more prominent choroidal thickening. Dr Kaya suggested that the main reason for increased choroidal flow was to dissipate the heat generated by metabolically active tumors. We believe that this is an attractive argument, well in agreement with our findings, and should be added to the list of possible explanations.

However, we are not sure why Dr Kaya believes that high choroidal blood flow should be explained solely in terms of metabolic heat regulation. First, whether natural choroidal blood flow can “provide enough blood supply for every situation, even for melanoma,” as Dr Kaya has stated, has not been substantiated or proven in study. Rapidly growing tumors generally have insufficient blood supply to meet metabolic demands and are thus marked by angiogenesis. Second, whether an increase in choroidal circulation provides metabolic requirements or dissipates metabolic heat are not mutually exclusive arguments. Third, our hypothesis included increased vascular permeability as another potential contributing factor to the increased choroidal thickness, possibly in association with increased levels of vascular endothelial growth factors from tumor-associated angiogenesis. We agree with Dr Kaya that increased vascular permeability may cause subretinal serous fluid accumulation. However, we do not agree that increased vascular permeability should not cause thickening of the choroid. For instance, there appears to be a direct topographic relationship between the area of choroidal thickening and the area of choroidal vascular hyperpermeability in a study with central serous chorioretinopathy.

We read with interest the 2 articles that Dr Kaya included in support of his argument. The first article illustrated the increased submacular choroidal thickness in eyes with extramacular toxoplamosis. Although Dr Kaya explained that the increased choroidal flow was due to inflammation-associated temperature rise, the authors of the article did not actually provide any explanation for the phenomenon, presumably because the article was in the brief reports format and inflammation is a complicated pathogenesis that can have multifaceted explanations. The second article illustrated the increased choroidal thickness following dynamic exercise. Increased choroidal blood flow could have occurred to distribute ocular heat generated by dynamic exercise. However, physical exercise causes elevation in systemic blood pressure and ocular perfusion pressure, which can cause an increase in choroidal blood flow and choroidal thickness, an explanation that was actually taken by the authors of the article.

In summary, we agree that increased choroidal blood flow can have roles in dissipating metabolic heat generated by choroidal melanoma. But tumorigenesis and inflammation in choroidal melanoma are complicated processes. We should not limit our views until one hypothesis is indisputably proven.

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Jan 6, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Reply

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