Rejection after corneal transplantationCorneal transplantation is a leading cause of graft failureGraft failure. The introduction of lamellar transplantationTransplantation techniquesTechnique has led to a significant reduction in rejection rates. Epithelial, subepithelial, and stromal rejections are rare immune reactions after penetrating keratoplastyKeratoplasty (PKP) or deep anterior lamellar keratoplastyKeratoplasty (DALK) and are usually of limited clinical importance. The greater risk for permanent functional graft failureGraft failure comes from endothelial rejection. Morphologically, they are characterized either by diffusely distributed keratic precipitates on the corneal graft or by a rejection lineRejection line (KhodadoustKhodadoust line) at the boundary between intact and rejected endothelium. After PKP, rejections with KhodadoustKhodadoust lines often originate from corneal neovascularizationsCorneal neovascularization. In contrast to PKP, KhodadoustKhodadoust lines are rare in rejections after Descemet membrane endothelial keratoplastyKeratoplasty (DMEKDMEK). After reducing the application frequency, prednisolone acetate or dexamethasone eyeEye drops are usually used for 1–2 years for prophylaxis of corneal graft rejectionGraft rejection. Overall, there is a very low risk of rejection after DMEKDMEK of approximately 2.5% within the first 5 years. Prophylaxis of rejection after DMEKDMEK can also be effectively performed with steroidsSteroid with lower glucocorticoid activity while reducing the risk of intraocular pressure decompensation.