A corneal transplant, also known as keratoplasty, is a surgical procedure that replaces a damaged or diseased cornea with healthy donor tissue. This procedure aims to restore vision compromised by corneal conditions. While often successful, corneal transplant rejection is a common complication that can threaten the long-term success of the transplant.
Understanding Corneal Transplant Rejection
Corneal transplant rejection occurs when the recipient’s immune system identifies the donor cornea as foreign tissue, initiating an immune response. Although the cornea has some “immune privilege” due to its lack of blood vessels and lymphatic drainage, this privilege is not absolute, and rejection can still occur. The immune system’s recognition of donor antigens, particularly Human Leukocyte Antigens (HLAs), triggers inflammation and potential damage to the transplanted tissue.
The immune response involves various cells, including T cells, B cells, macrophages, and dendritic cells. Antigen-presenting cells (APCs) transport donor antigens to nearby lymph nodes, activating naive T cells. These activated T cells, especially CD4+ T cells, then migrate to the cornea to attack the graft.
Rejection episodes manifest in different ways, with acute and chronic forms being the primary types. Acute rejection is the most frequent form and typically occurs within weeks to months after surgery. Chronic rejection is a slower, progressive process that can develop months or even years following the transplant, often leading to a slow decline in vision over time.
Recognizing the Signs of Rejection
Recognizing the signs of corneal transplant rejection is important for timely intervention. Patients may experience persistent redness in the affected eye, which often indicates inflammation within the transplanted cornea.
Increased sensitivity to light, known as photophobia, is another common symptom. This discomfort can range from mild to severe, making bright environments difficult to tolerate. Any noticeable decrease in vision, such as blurring, haziness, or a general loss of clarity, should also be considered a warning sign.
Discomfort or aching in the eye, ranging from a dull ache to a sharper pain, can accompany other symptoms. Patients might also report excessive tearing or a feeling as if a foreign object is present in their eye. If any of these symptoms appear, seeking immediate medical attention from an ophthalmologist is important, as early diagnosis and treatment significantly improve the chances of reversing the rejection episode.
Diagnosis and Treatment Approaches
The diagnosis of corneal transplant rejection is primarily made by an ophthalmologist through a slit-lamp examination. During this examination, the doctor observes specific signs within the cornea, such as swelling, deposits, or new blood vessel growth. A visible line, sometimes called a Khodadoust line, may also appear, marking the boundary between healthy and affected tissue.
Corticosteroids are the primary treatment for acute graft rejection. These medications suppress the immune system’s inflammatory response. They can be administered as eye drops, oral medications, or injections, depending on the rejection’s severity. For epithelial and subepithelial rejections, topical corticosteroids may be used multiple times a day, with dosage gradually reduced over several weeks.
In more severe or recurrent cases of rejection, or for high-risk patients, immunosuppressants may be prescribed. These medications, such as cyclosporine A or tacrolimus, further suppress the immune system’s activity to prevent it from attacking the donor tissue. Patients receiving systemic immunosuppressants require close monitoring of their liver and kidney function.
Managing potential complications is also part of treatment. For example, corticosteroids can sometimes increase eye pressure, requiring additional medication. If rejection is irreversible and results in significant vision loss, a re-transplantation may be considered. However, repeat transplants carry a higher risk of subsequent rejection due to increased immune sensitization.
Preventing Rejection and Long-Term Care
Preventing corneal transplant rejection involves consistent adherence to prescribed medications and regular professional monitoring. Patients are typically prescribed eye drops, often corticosteroids or immunosuppressants, which must be used as directed for an extended period, sometimes lifelong. This continuous medication regimen helps suppress the immune response and minimize the risk of the body rejecting the new cornea.
Routine follow-up appointments with the ophthalmologist are also important. These visits allow the doctor to monitor the eye’s health, assess the clarity of the graft, and detect any early signs of rejection not yet noticeable to the patient. Early detection allows for prompt treatment, which significantly increases the likelihood of successfully reversing a rejection episode.
Protecting the eye from injury and infection is another preventative measure. Patients should avoid rubbing their eyes and consider wearing protective eyewear during activities that could cause impact or expose the eye to irritants. Prompt treatment of any eye infections is also important, as inflammation can trigger an immune response that increases rejection risk.
The long-term outlook for corneal transplant patients generally involves ongoing vigilance. While many transplants are successful, the possibility of future rejection episodes remains, even years after the initial surgery. With consistent care, adherence to medication, and regular follow-ups, many patients maintain good vision for extended periods.