Corneal transplantation was the first organ transplantation to be successful because normal corneas have no blood vessels or lymphatic vessels, and the graft is not easily recognized by the immune system of the patient’s body, thus generally not causing a rejection reaction. Just as blood transfusion may cause allergic reaction between different individuals, allogeneic corneal transplantation may also cause immune rejection, especially when the graft is large, during inflammation, when there is neovascularization in the cornea, and when the antigens of corneal tissues are very different, the antigens of the allogeneic cornea can be recognized by the immune system of the patient, and the immune system will further produce allergic lymphocytes and antibodies against the graft, and the lymphocytes and antibodies will then attack and reject the graft. The lymphocytes and antibodies then attack and reject the graft, resulting in degeneration, clouding, scar formation and blindness.