Illustration of a corneal transplant. The cornea is a fine membrane consisting of 3 layers, the epithelium, the stroma and the endothelium. Each can be affected, sometimes all three. Depending on the severity, treatment consists of carrying out a partial or total transplant to replace this fine membrane. The transplant uses a human graft (top right). An alternative to this type of transplant is an artificial cornea transplant (lower right). Both operations take place under local or general anesthetic and last around 45 minutes.