A cornea transplant, formally known as keratoplasty, replaces diseased or damaged corneal tissue with healthy donor tissue. The cornea is the clear, outermost layer at the front of the eye, focusing light for clear vision. When the cornea becomes cloudy, scarred, or distorted due to disease or injury, a transplant is often the only option to restore transparency and improve sight. This intervention is a highly successful form of tissue transplantation, and understanding the factors that influence the survival of the transplanted tissue helps quantify the likelihood of a positive, long-term outcome.
Overall Success Rates and Defining Graft Survival
The success of a cornea transplant is measured by “graft survival,” meaning the donor cornea remains clear and functions adequately to support vision. Graft survival focuses on the long-term clarity and function of the transplanted tissue, distinct from the surgical completion itself. For low-risk cases, such as those performed for keratoconus, the one-year survival rate often exceeds 90%.
The long-term outlook is more nuanced. Graft survival for uncomplicated first-time transplants decreases to an average of about 62% at the ten-year mark. This statistic is heavily influenced by the patient’s initial risk profile. High-risk recipients, who have pre-existing inflammation or extensive blood vessel growth, can have significantly lower survival rates, sometimes falling to between 35% and 70% at two years. Graft failure is the irreversible loss of corneal clarity, usually caused by the death of donor endothelial cells responsible for keeping the cornea clear of fluid.
Success Rates Based on Transplant Type
The specific surgical technique employed is a primary determinant of the transplant’s success rate and long-term prognosis. Older, full-thickness procedures, such as Penetrating Keratoplasty (PKP), replace all layers of the cornea. PKP is necessary for deep scarring or distortion, and for low-risk indications like keratoconus, it can achieve excellent long-term survival, sometimes over 90% at ten years.
Newer, partial-thickness techniques, known as lamellar keratoplasty, selectively replace only the diseased layer. Endothelial Keratoplasty (EK), including Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) and Descemet’s Membrane Endothelial Keratoplasty (DMEK), is performed when only the innermost layer (the endothelium) is damaged, such as in Fuchs’ dystrophy. These partial-thickness procedures are less invasive than PKP, resulting in faster visual recovery and a reduced risk of immune rejection.
DMEK, which transplants the thinnest layer, has demonstrated the lowest long-term rejection rate, reported as low as 10% at ten years, compared to 19% for DSAEK. DMEK can have a higher risk of early complication, such as graft detachment, which may require an additional procedure called a “rebubble” to reposition the tissue. Despite this, EK procedures are the preferred method for endothelial failure due to their overall safety profile and superior visual outcomes.
Patient and Disease Factors Affecting Prognosis
The long-term outlook is shaped by variables related to the recipient’s eye health and underlying disease. Patients are categorized as “low-risk” or “high-risk” based on these pre-existing conditions, which affect the likelihood of graft rejection or failure. The underlying cause of corneal failure is a primary factor; grafts performed for severe conditions like chemical burns or active infections have a poorer prognosis than those for non-inflammatory diseases like keratoconus.
The presence of corneal neovascularization (new blood vessel growth) is a powerful indicator of high risk. These vessels introduce immune cells into the area, breaching the cornea’s natural immune-privileged status and greatly increasing the chance of rejection. A history of previous transplant failure, especially if due to rejection, makes subsequent transplants much more vulnerable to the same outcome.
Other complicating factors that raise the risk profile include pre-existing glaucoma, ocular surface disease, or a history of complex intraocular surgeries. The patient’s commitment to the post-operative regimen is also influential, as strict adherence to prescribed immunosuppressive eye drops helps maintain the graft’s clarity. These underlying issues, independent of the surgical technique, are used by physicians to predict the long-term stability of the transplanted tissue.
Recognizing and Treating Graft Rejection
Graft rejection is the most frequent cause of late-stage transplant failure. It occurs when the recipient’s immune system recognizes the donor tissue as foreign and mounts an attack. This immune response targets the donor endothelial cells; since these cells do not regenerate, their destruction leads to fluid accumulation and irreversible clouding of the graft. The risk of rejection is highest in the first year but persists indefinitely, requiring lifelong vigilance.
Patients are educated to watch for symptoms remembered by the acronym RSVP: Redness, Sensitivity to light, Vision decrease, and Pain. Prompt recognition is important because treatment success is tied to how quickly therapy is initiated after symptoms appear. When rejection is suspected, the immediate protocol involves administration of high-dose topical corticosteroids, such as prednisolone acetate 1% or dexamethasone 0.1%.
These drops are applied hourly while the patient is awake for the first few days to suppress the immune attack rapidly. For severe cases or in high-risk patients, treatment may be escalated to include systemic steroids, such as oral prednisone, or steroid injections near the eye. If the rejection episode is caught and treated early, the graft can often be saved, with reversal rates reported to be as high as 50% to 94%.