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We read with great interest the paper by Li et al about staining of the internal limiting membrane (ILM) and epiretinal membrane (ERM) with trypan blue (TB).1 We would like to comment on one aspect of this paper, when the authors claimed that a good staining of both the ILM and the ERM was achieved with TB. We disagree that ILM is stained by TB, and propose that TB only stains the ERM, not the ILM.
The authors affirm “ILM staining” with TB as they observed histologically the presence of ILM in four eyes with macular holes at stage III and IV. In one of those eyes, immunohistochemistry was performed, and an epiretinal membrane was observed. In the other three cases, immunohistochemistry examination was not performed because of insufficient tissue. Most of the stage III and IV macular holes are known to be associated with an epiretinal membrane,2 and probably an ERM would be seen in addition to the ILM in those three cases if immunohistochemistry for glial elements were performed. Therefore, we believe that TB stained the ERM associated with the macular holes, but not the ILM. In their study, staining with TB of seven patients with idiopathic epiretinal membrane was successfully performed. ERM of proliferative vitreoretinopathy is also reported to be well stained by TB.3 We speculate that TB has binding affinity to some of the glial cell elements of the highly cellular ERMs, either those associated with macular holes or not.
Indocyanine green (ICG) is another new dye for intraocular staining that has gained wide acceptance among retina surgeons in the past few years.4 In contrast with the cellular affinity of TB, ICG stains the acellular ILM, because of the fast binding of ICG to collagen proteins of the ILM. ERM tends to be stained negatively by ICG, well because the hydrophilic ICG does not penetrate cell membranes easily.5
TB staining seems to be a good alternative to ICG staining in the surgical management of macular diseases. Further studies are warranted on the intraocular kinetics of that dye.