Ghaffari R, et al. - A prospective interventional case series is carried out to assess the safety and effectiveness of tacrolimus eye drop as adjunctive therapy in the treatment of severe corneal endothelial rejection after penetrating keratoplasty refractory to corticosteroids. The outcome suggests tacrolimus eye drops may be able to play an adjunctive therapeutic role in patients with severe corneal endothelial rejection refractory to conventional steroid treatment. To further explore the role of tacrolimus in this setting, controlled studies are needed.