Dear Sir,
We read with great interest the article by Goud et al. concerning choroidal changes in central serous chorioretinopathy (CSCR) patients after the water-drinking test (WDT).1
We congratulate the authors for their idea to utilize the WDT, previously used as a diagnostic tool for glaucoma, to analyze its effect on different choroidal parameters in acute CSCR, chronic CSCR, nonaffected fellow, and healthy eyes, but we would like to make some comments.
Among the evaluated parameters, the authors tested the choroidal vascularity index (CVI) obtained from a binarization of a grayscale optical coherence tomography (OCT) image in an attempt to better distinguish the luminal from the stromal choroidal area.2
We are aware that CVI has been largely used in the international literature, but in our opinion, the binarization has a limitation because it can be influenced by the so-called “blooming effect.”
The blooming effect, which is well-known in the echographic area, is an artifact that makes it difficult to acquire accurate measurements of the structures being examined, especially if they are small in size, as in the case of ocular and orbital structures.2,3 The signal amplification causes this effect. When utilizing high signal amplification, the image will look brighter and the amount of white pixels will increase; however, when using a low level, the reverse will occur.4,5
This artifact appears to be present in OCT as well.
We are afraid that this effect could also influence the binarization utilized in the CVI evaluation, increasing the low reflective areas, considered to be the luminal ones, when a low amplification is used, and reducing them when the amplification is higher, making the results unreliable.
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Conflicts of interest
There are no conflicts of interest.
REFERENCES
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