A cornea transplant, also known as keratoplasty, replaces a damaged or diseased cornea with clear, healthy donor tissue. The cornea is the transparent, dome-shaped front surface of the eye, and its clarity is fundamental for focused vision. While corneal transplantation is highly successful, the body’s immune system can identify the new tissue as foreign, leading to graft rejection. This immune response remains the primary complication that can cause graft failure and vision loss.
How the Immune System Reacts to the New Cornea
The body’s immune system distinguishes between its own cells and foreign invaders by recognizing antigens on the donor tissue. The graft contains Human Leukocyte Antigens (HLAs), which the recipient’s immune cells, primarily T-lymphocytes, perceive as “non-self.” These T-cells become activated after recognizing the foreign antigens, triggering an inflammatory attack intended to eliminate the perceived threat. This sustained immunological assault attempts to destroy the new tissue, resulting in a loss of the graft’s clarity. If the inflammation is not stopped promptly, the damage can become irreversible, leading to graft failure.
Recognizing the Signs of Rejection
Patients should monitor for the signs of rejection, summarized by the acronym RSVP: Redness, Sensitivity to light (photophobia), Vision decrease, and Pain. Any of these symptoms appearing suddenly require immediate medical attention. Redness, particularly around the edge of the graft, is a frequent sign of inflammation, and the eye may also become intensely sensitive to bright light.
A decrease in visual clarity, often described as cloudy or hazy vision, is the most concerning symptom. This clouding suggests swelling of the donor cornea caused by dysfunction of the endothelium, the innermost layer of cells responsible for keeping the cornea clear. While a surgeon can observe physical signs, the patient-reported change in vision is the most significant symptom necessitating an urgent examination. Eye pain or a persistent foreign body sensation may accompany the other signs.
Unique Characteristics Affecting Cornea Success
The cornea is unique among transplanted tissues because it benefits from corneal immunoprivilege, which contributes to its high success rate. This privilege is primarily due to the central cornea’s lack of direct blood and lymphatic vessels (avascularity). Without these vessels, circulating immune cells cannot easily enter the graft to attack the foreign tissue.
Despite these protective factors, certain conditions compromise immunoprivilege, significantly increasing the rejection risk. High-risk factors include the growth of new blood vessels into the central cornea (neovascularization), a history of severe ocular inflammation, or a need for multiple previous corneal grafts. When blood and lymphatic vessels invade the cornea, they create a pathway for immune cells to traffic into the graft, making rejection much more probable.
Prevention Protocols and Emergency Treatment
Preventing corneal graft rejection relies on the long-term use of topical immunosuppressive medications, most commonly corticosteroid eye drops. These drops suppress the localized immune response, preventing T-cells from attacking the donor tissue. Patients typically use these drops for many months or years, with the dosage gradually tapered by the surgeon based on the eye’s stability.
If a rejection episode is suspected, the treatment shifts to an aggressive regimen aimed at quickly reversing the immune attack. This emergency treatment usually involves increasing the frequency and dose of topical steroid drops, sometimes to as often as every hour. In severe or rapidly progressing cases, oral steroids or intravenous corticosteroid injections may be administered. Prompt identification and treatment can often successfully reverse the attack, saving the graft and preserving vision.