Keratoconus is a progressive eye condition that affects the cornea, the clear, dome-shaped front surface of the eye. This disorder causes the cornea to gradually thin and bulge into an irregular, cone-like shape, which distorts how light enters the eye and significantly impairs vision. For individuals with advanced keratoconus, where vision can no longer be adequately corrected with less invasive methods, corneal transplantation becomes a necessary surgical intervention. This procedure aims to restore a more regular corneal shape, thereby improving visual function.
Understanding Keratoconus and When Transplantation is Needed
Keratoconus begins during puberty and can progress into a person’s mid-30s, causing the cornea to become thinner and more irregular. This structural change leads to blurred and distorted vision, including ghosting, halos around lights, and multiple images. Initially, vision changes can be managed with eyeglasses or specialized contact lenses, such as rigid gas permeable (RGP) or scleral lenses, which help smooth the irregular corneal surface.
When non-surgical treatments no longer provide functional vision, or if the cornea becomes excessively thin, scarred, or unstable, corneal transplantation is considered. Corneal scarring may result from long-term stress or acute swelling (hydrops). If patients can no longer tolerate wearing contact lenses due to discomfort or poor fit, transplantation is considered. About 5-10% of individuals with keratoconus require a corneal transplant.
Types of Corneal Transplants for Keratoconus
Two primary surgical approaches are employed for keratoconus corneal transplantation: Penetrating Keratoplasty (PK) and Deep Anterior Lamellar Keratoplasty (DALK). Each technique replaces a portion of the diseased cornea with healthy donor tissue, differing in the layers transplanted.
Penetrating Keratoplasty (PK) involves a full-thickness transplant. The entire central part of the patient’s diseased cornea is removed and replaced with a similarly sized disc of healthy donor cornea. This procedure is chosen for severe cases, especially if there is significant scarring or damage to the innermost layers. The new donor cornea is sewn into place with sutures, which remain for 6 to 18 months, sometimes up to 2 years. PK has a high success rate, with graft survival rates exceeding 90% after 10 years, and it can improve vision.
Deep Anterior Lamellar Keratoplasty (DALK) is a partial-thickness transplant that replaces only the front layers of the cornea, specifically the diseased corneal stroma, while preserving the patient’s own innermost layer (Descemet’s membrane and endothelium). This technique is preferred when the patient’s endothelium, which helps keep the cornea clear, is healthy. An advantage of DALK over PK is a reduced risk of endothelial immune rejection, as the patient retains their own endothelial cells. DALK can also lead to faster healing and a less fragile eye post-operation. However, it is a technically demanding procedure, and in a small percentage of cases, the surgery can be converted to a full-thickness PK if the thin back layers of the cornea cannot be preserved intact.
The Surgical Procedure and Recovery
Corneal transplantation for keratoconus is performed as a day-case procedure, with patients going home the same day. The surgery is performed under general anesthesia for patient comfort. During the procedure, the surgeon removes the abnormally shaped central part of the patient’s cornea using specialized instruments, often a trephine (7.0 to 8.5 mm in diameter). A matching piece of healthy donor corneal tissue, slightly oversized for a proper fit, is then positioned and secured with sutures. These sutures are placed to optimize fit and minimize post-operative astigmatism.
Immediately after surgery, an eye patch or shield is placed over the treated eye to protect it. Patients can expect mild discomfort, a gritty sensation, and tearing, along with blurry or hazy vision in the first few weeks. Eye drops, including antibiotics to prevent infection and corticosteroids to reduce swelling, inflammation, and prevent rejection, are prescribed. Light duty activities may be possible after 3-6 weeks, with normal activity resuming around 3 months. Heavy exercise and lifting are restricted for the first several weeks. Visual improvement is gradual and can take several months, up to a year, to stabilize. Sutures are removed over time, typically 6 to 18 months, or up to 2 years after PK.
Life After Transplant
After a corneal transplant for keratoconus, long-term care and monitoring are necessary to maintain graft health and achieve an optimal visual outcome. Regular follow-up appointments with the eye doctor are important to monitor healing, adjust medication, and check for complications like graft rejection or infection. Anti-rejection eye drops, corticosteroids, are required for months or years, with dosage managed by the surgeon.
Vision improvement can continue for an extended period, for months to a year or longer, with stable vision achieved after all sutures are removed. While some patients may achieve good uncorrected vision, the majority will still require glasses or contact lenses for optimal clarity due to residual astigmatism or other refractive errors. The average life of a corneal transplant for keratoconus is good, with graft survival rates over 90% after 10 years and an average lifespan of 15-20 years. Patients should remain vigilant for symptoms of rejection, such as redness, pain, light sensitivity, or blurred vision, as prompt treatment with steroid drops can reverse rejection episodes.