Trypan blue is an azo dye solution that effectively stains basement membranes such as the anterior lens capsule and Descemet's membrane.1 In Descemet's membrane endothelial keratoplasty (DMEK), where the host Descemet's membrane and corneal endothelium are initially removed, trypan blue is used to stain the donor graft before injection to provide visibility during the unscrolling process in the anterior chamber. Trypan blue can also be injected after the descemetorrhexis and before graft injection to visualize any irregular tags or retained Descemet's membrane, both of which may increase the risk for graft detachment.