How Is a Corneal Transplant Performed? Step-by-Step Procedure Guide

A corneal transplant is an operation in which damaged or diseased corneal tissue is replaced with healthy donor tissue. Although the basic goal is the same, the actual procedure varies depending on which part of the cornea is affected. Some patients need the entire thickness of the cornea replaced, while others need only a specific layer.

Modern corneal surgery therefore does not always involve removing the whole cornea. Techniques such as penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK), and endothelial keratoplasty such as DMEK or DSAEK allow surgeons to replace the part of the cornea that is diseased while preserving healthy tissue whenever possible.

Understanding how the operation is performed can make the process easier to follow if you are considering corneal transplant surgery. The exact steps, however, depend on your diagnosis and the type of transplant recommended by your ophthalmologist.

What Happens Before a Corneal Transplant?

The procedure begins well before entering the operating room. Your ophthalmologist first needs to determine whether transplantation is appropriate and which type of surgery is best suited to your corneal condition.

The preoperative assessment may include:

• A detailed examination of the cornea and the rest of the eye
• Visual acuity testing
• Corneal measurements and mapping
• Assessment of corneal thickness and shape
• Evaluation of the retina and optic nerve when necessary
• Review of previous eye surgery or corneal transplantation

The surgeon also considers whether the disease affects the front, middle or inner layers of the cornea. This helps determine whether a full-thickness or partial-thickness transplant is appropriate.

Where Does the Donor Cornea Come From?

The transplanted tissue comes from a donated human cornea. Donor corneas are collected through an eye bank and undergo screening and evaluation before being released for transplantation.

The tissue is examined to determine whether it is suitable for the particular type of transplant. For example, endothelial procedures require donor tissue with an adequate number and quality of healthy endothelial cells. The donor cornea is then prepared according to the surgical technique that will be used.

Step 1: Anesthesia Is Given

Corneal transplant surgery can be performed using local or general anesthesia depending on the patient's circumstances, the type of procedure and the surgeon's preference.

With local anesthesia, the eye is numbed so that you do not feel the surgical procedure. Medication may also be given to help you remain relaxed. In some situations, general anesthesia may be used so that you are completely asleep during surgery. A special device is used to gently keep the eyelids open during the procedure.

Step 2: The Damaged Corneal Tissue Is Identified

The surgeon carefully identifies the portion of the cornea that needs to be replaced. The amount of tissue removed depends on the type and extent of disease.

This is an important distinction between different transplant procedures. In a full-thickness transplant, the diseased corneal tissue is removed through its full depth. In a partial-thickness procedure, the surgeon removes only the affected layers while preserving healthy tissue whenever possible.

Step 3: The Appropriate Type of Corneal Transplant Is Performed

There are three broad approaches used in modern corneal transplantation.

Penetrating Keratoplasty: Full-Thickness Corneal Transplant

Penetrating keratoplasty (PK) replaces the full thickness of the cornea. It may be considered when significant scarring or damage affects the entire cornea or multiple layers and a partial transplant would not be suitable.

During the procedure:

1. The surgeon marks the area of the cornea to be removed.
2. A specialized circular surgical instrument is used to remove the damaged central portion.
3. A matching section of healthy donor cornea is prepared.
4. The donor tissue is positioned in the opening.
5. Fine sutures are used to secure the graft in place.

Deep Anterior Lamellar Keratoplasty: Replacing the Diseased Front Layers

Deep anterior lamellar keratoplasty (DALK) is a partial-thickness transplant. It is used for selected conditions in which the front and middle layers of the cornea are diseased but the patient's own endothelium remains healthy.

During DALK, the surgeon removes the affected stromal tissue while preserving the patient's Descemet's membrane and endothelial layer. Donor corneal tissue containing the appropriate stromal layers is then placed over the remaining healthy tissue and secured.

This approach can be useful for selected patients with conditions such as keratoconus or certain corneal scars. Because the patient's healthy endothelial cells are retained, DALK has a different risk profile from a full-thickness transplant.

Endothelial Keratoplasty: Replacing the Inner Corneal Layer

Endothelial keratoplasty is used when the main problem is in the innermost layer of the cornea, particularly the endothelial cells that help keep the cornea clear. Common forms include:

• DMEK – Descemet membrane and endothelial cells are transplanted.
• DSAEK/DSEK – The donor tissue includes the endothelium, Descemet's membrane and a thin layer of posterior stroma.

Unlike a full-thickness transplant, these procedures use a much smaller donor tissue graft and leave most of the patient's cornea untouched.

Step 4: The Donor Tissue Is Positioned

The way donor tissue is positioned depends on the transplant technique. For a full-thickness transplant, the donor corneal button is placed directly into the opening created by removing the diseased tissue. For DALK, the donor stromal tissue is positioned over the patient's preserved deeper corneal layers.

For endothelial transplantation, the delicate donor tissue is inserted through a small incision and unfolded or positioned against the inner surface of the cornea. The surgeon carefully confirms its orientation before using an air or gas bubble to support it.

Because endothelial grafts are extremely thin, positioning them correctly is a particularly delicate part of the procedure.

Step 5: The Graft Is Secured

The method used to secure the transplant depends on the type of surgery. In penetrating keratoplasty, fine sutures are generally used around the edge of the donor cornea to hold the graft securely in place.

Some partial-thickness procedures require fewer sutures or none at all. In endothelial keratoplasty, an air or gas bubble is generally used to keep the donor layer against the recipient cornea while the graft attaches.

This difference is one reason why recovery and postoperative care can vary significantly between transplant techniques.

Step 6: The Eye Is Protected After Surgery

At the end of the procedure, the eye may be covered with a protective patch or shield. Depending on the type of surgery and the patient's condition, prescribed eye drops are started to reduce inflammation and prevent infection.

Most corneal transplants are performed as outpatient procedures, meaning many patients can return home on the same day. However, the exact plan depends on the operation and the patient's medical circumstances.

You will generally need someone to accompany you home because vision will be temporarily impaired and you should not drive immediately after surgery.

How Long Does Corneal Transplant Surgery Take?

The duration varies depending on the type and complexity of the transplant. A full-thickness transplant involves removing and replacing a larger section of the cornea, while endothelial procedures use a much smaller graft and incision.

Your surgeon can provide a more accurate estimate based on the specific procedure planned for your eye. The length of the operation, however, is not the same as the length of recovery. Even when surgery itself is completed relatively quickly, the transplanted cornea may need weeks or months to heal and stabilize.

What Is Recovery Like After a Corneal Transplant?

Early recovery may involve redness, watering, mild discomfort and blurred vision. These symptoms generally improve as healing progresses, although visual recovery can take considerably longer than the initial wound healing.

You may be instructed to:

• Use prescribed eye drops exactly as directed
• Avoid rubbing or pressing on the eye
• Protect the eye with glasses or a shield when advised
• Attend scheduled follow-up appointments
• Avoid strenuous activities until cleared by your surgeon

The recovery period depends strongly on the procedure. Some endothelial transplants can provide relatively rapid visual improvement, while vision after a full-thickness transplant may continue changing for many months. After penetrating keratoplasty, sutures may remain for an extended period while the graft heals and the corneal shape stabilizes.

How Is a Corneal Transplant Different From Other Eye Surgeries?

One important difference is that the surgeon is working with donated human tissue rather than simply reshaping or removing the patient's own tissue.

The transplanted cornea must remain clear, attach properly and function normally after surgery. The patient's immune system can also recognize donor tissue as foreign, which means graft rejection remains an important possible complication.

Because of this, follow-up and postoperative eye-drop treatment are important even after the eye initially appears to be healing well.

Why Is Only the Damaged Layer Replaced When Possible?

Modern corneal transplantation increasingly focuses on replacing only the diseased tissue when the remaining cornea is healthy.

This approach can preserve more of the patient's own cornea and, depending on the procedure, may reduce some of the risks associated with full-thickness transplantation.

For example, a patient whose disease is limited to the endothelium may not need the entire cornea replaced. An endothelial transplant can replace the dysfunctional inner layer while leaving the patient's healthy outer corneal tissue intact.

The choice is therefore based on the location and extent of disease rather than using the same transplant technique for every patient.

The Bottom Line

A corneal transplant is performed by replacing damaged corneal tissue with healthy donor tissue, but the exact operation depends on which layer of the cornea is diseased. A full-thickness penetrating keratoplasty replaces the entire cornea, while DALK and endothelial keratoplasty allow surgeons to replace only selected layers when the remaining tissue is healthy.

The procedure generally involves careful preoperative assessment, anesthesia, removal of the diseased tissue, placement of donor tissue and securing the graft using sutures or an air or gas bubble depending on the technique.

Most patients can return home the same day, but recovery continues well beyond the operation itself. Eye drops, protective measures and regular follow-up are important, and visual recovery can take weeks or months depending on the transplant.

The most appropriate technique is determined by the cause of the corneal disease, the layer affected, the condition of the remaining cornea and the overall health of the eye. This layer-specific approach allows many patients to receive a transplant without replacing healthy portions of their own cornea.