Response to comments on: Subretinal drusenoid deposits versus drusen on multicolor imaging

Dear Editor, We thank the authors for reading and making a few comments on our essay on the differences on multicolour imaging between subretinal drusenoid deposits (SDD) and drusens.[12] The authors in their reply try to make a point that the differences on the multicolour imaging between drusens and SDDs are merely due to the location of the deposits in relation to the retinal pigment epithelium (RPE). The authors have also cited an article by Spaide and Curcio to support this theory.[3] It is important to note that the imaging modalities studied in that paper were colour fundus images, fluorescein angiography, autofluorescence and spectral-domain optical coherence tomography images. Multicolour imaging is based on the property of reflectance which is the measure of the proportion of light of a given wavelength striking a surface which is reflected off it.[4] We believe that just the location of the material above or below the RPE may not contribute to the multicolour imaging findings. In addition, there are a number of factors such as the wavelength of the light used, retinal thickness, height of the drusen, the presence of RPE atrophy and the content of the drusen material can contribute to the multicolour imaging features. Though the drusens are located underneath the RPE, they can still be identified on the green and blue reflectance images in some cases, if they are tall and elevated. The absence of esterified cholesterol in an SDD will change the reflectance properties of the material and also show variations in the multicolour imaging findings. Thus, we believe that there are a number of factors which contribute to the multicolour imaging findings in SDD and drusen, with the esterified cholesterol content in the drusen being the most important of all. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.