It is well known that most corneal blindness can be restored by corneal transplantation. With the continuous improvement of ophthalmic equipment and instruments, the success rate of penetrating keratoplasty has reached more than 85%. Most of the unsuccessful operations are caused by rejection.
Especially for patients with vascularized cornea, large grafts transplantation, partial center of grafts and chemical injury of cornea, more than 60% of them fail to operate due to rejection after operation. In recent years, the international ophthalmology community has called these patients high-risk corneal transplant patients.
What are the high risk factors leading to corneal transplantation? Besides corneal transplantation, can they restore their vision by other methods?
There are roughly five high-risk factors leading to corneal transplantation.
Corneal neovascularization
Corneal neovascularization is the most important and common factor in high-risk corneal transplantation. Corneal neovascularization is often caused by herpes simplex virus infection in the late stage of corneal degeneration, chemical eye injury (especially after alkali burn), and severe dry eye disease.
Numerous studies have confirmed that the vascularized graft bed not only increases the rejection rate after surgery, but also reduces the survival rate of the graft. The number of corneal neovascularization was positively correlated with the rejection after surgery. According to statistics, the rate of transplant failure caused by immune rejection of the seriously neovascularized corneal implantation bed is as high as 60%, while the rejection rate of the corneal implantation bed without blood vessels is only 0~10%.
Multiple migration failures
After the failure of the first corneal transplantation, the failure rate is more than 25%. The more the number of times, the higher the failure rate. But the exact mechanism of rejection failure is not very clear. Many people believe that the patient's immune surveillance system is more sensitive to non-own HLA antigen.
Bilateral penetrating keratoplasty
Researchers used to think that patients with bilateral penetrating keratoplasty were high-risk patients. In clinical practice, patients with bilateral keratoplasty received different HLA antigens from donor grafts, which would stimulate the systemic immune system and produce immune response.
Large graft and eccentric transplantation
The central cornea without blood vessels is considered to be the most important factor for the success of corneal transplantation, while the large graft and eccentric center increase the chance of contact between the graft and limbal vessels, which greatly increases the rejection rate, which has been accepted by most scholars. However, the relationship between graft size and rejection is difficult to reach a consistent conclusion due to the different cases selected by each expert. For example, when selecting large grafts, it is often caused by serious infection or other eye complications, which leads to postoperative failure.
In addition to immune response, anterior synechia of iris, secondary glaucoma and re-infection of graft are also inseparable reasons. However, patients with eccentric transplantation often have preoperative corneal lesions close to the limbus, sometimes accompanied by other lesions, and the reasons for the failure of surgery are also complex.
At present, there is a relatively consistent consensus in clinical practice that in the central area of the cornea, it is safer to have a graft smaller than 8 mm.
Blood transfusion, pregnancy, immunization and other transplant recipients
In the past, people who have received blood transfusion or pregnant women were considered as high-risk corneal transplant patients, because the blood cells or fetal factors imported by these patients made the systemic immune system in a sensitized state. However, some scholars hold negative opinions, and there is no final conclusion at present.
The researchers performed penetrating keratoplasty on 5 patients who had been vaccinated with influenza and hepatitis vaccine before surgery, and all of them had rejection within 24 hours to 8 weeks. Another group of researchers had performed penetrating keratoplasty on a patient who underwent skin transplantation, and the grafts had acute rejection within one week. Some people believe that this is because the systemic immune system has been sensitized in advance, or the antigen-antibody complex has been deposited in the uvea.
In short, the rejection of high-risk corneal transplant patients after surgery is the main reason for the failure of surgery, and it is also a rather thorny problem in the field of ophthalmology at present. People have paid more and more attention to it. If people solve the immune problem of high-risk transplantation, the time for human to use xenogeneic cornea for penetrating keratoplasty is not far away.
Of course, nowadays, with the introduction and application of Mich artificial cornea, it is no longer difficult for high-risk corneal transplant patients to recover their eyesight.
Last week, two patients had completed the second phase operation of Mich artificial cornea in the General Hospital of the People's Liberation Army. Among them, the vision of patients who were blind due to immune system diseases increased from 0.3 before operation to 0.8 after operation, and the vision of another patient who was blind due to alkali burns has reached 1.0 after operation.
It is enough to prove that Mich artificial cornea provides a new way for clinical treatment of patients with contraindications of traditional corneal transplantation (so-called high-risk corneal transplantation patients). If you or your family and friends in front of the screen are high-risk patients with corneal transplantation, you can call the official customer service telephone number of Mich Medical: 400-111-8801, and a professional doctor will evaluate for you.