Different Types of Corneal Transplants

A corneal transplant is a surgical procedure that restores vision when a disease or injury alters the transparency or structure of the cornea. It is one of the most commonly performed transplant operations in the world, with a high success rate. It can take several forms depending on the area of the cornea affected.

Penetrating keratoplasty

Penetrating keratoplasty is the oldest corneal transplant technique. It involves replacing the full thickness of the cornea with a circular graft from a donor. This method is indicated when the cornea is damaged throughout its thickness, as in certain dystrophies, advanced keratoconus, or after severe trauma. Although effective, it is associated with slower visual recovery and a higher risk of rejection.

Lamellar keratoplasties

Lamellar keratoplasties are more modern and selective techniques. They replace only the diseased part of the cornea while keeping the healthy layers, which reduces the risk of complications.

Deep Anterior Lamellar Keratoplasty (DALK)

DALK is a technique that replaces the front layers of the cornea, leaving the endothelium (the inner layer) intact. This transplant is recommended for patients with keratoconus, stromal scarring or stromal dystrophies. It preserves the patient’s own endothelium, thereby reducing the risk of immune rejection.

DALK, the English-language term for “Deep Anterior Lamellar Keratoplasty”

DALK is the English-language term for what French-speaking surgeons call KLAP. It relies on careful dissection of the corneal stroma down to Descemet’s membrane without perforating it. This technique demands great surgical expertise, but it offers better preservation of the native eye and gradual visual recovery.

Endothelial transplant

Unlike DALK, an endothelial transplant is used when only the inner layer of the cornea is damaged, notably in cases of Fuchs’ dystrophy or endothelial decompensation after surgery.

DMEK, the English-language term for “Descemet Membrane Endothelial Keratoplasty”

DMEK is one of the most advanced endothelial transplant techniques. It involves replacing only Descemet’s membrane and the endothelium. This transplant offers rapid visual recovery and an extremely low rejection rate. However, it requires very precise operating conditions and rigorous technical mastery.

The transplant patient’s journey

Before any transplant, a complete ophthalmological assessment is performed. The patient is placed on a waiting list to receive a compatible cornea. The operation is generally performed under local or general anesthesia, depending on the technique chosen. After the transplant, the patient must follow a local immunosuppressive treatment (eye drops) and attend regular check-ups for several months, or even years. Adherence to this care is essential for graft survival and optimal visual recovery.

Main complications of corneal transplants

Despite technical advances, corneal transplantation carries certain risks of complications, classified as intraoperative and postoperative complications.

Intraoperative complications

Open-sky expulsive hemorrhage

This serious complication occurs when there is a sudden loss of intraocular pressure during the procedure, leading to partial or total expulsion of the contents of the eye. It is a rare but dreaded surgical emergency.

Other complications

Other intraoperative complications include accidental perforations, intraocular bleeding or damage to the lens, particularly during deep lamellar transplants.

Postoperative complications

Graft rejection

Rejection is an immune response by the body against the graft. It can occur within weeks, months or years after the transplant. It shows up as decreased vision, pain, eye redness and photophobia. Prompt treatment with corticosteroids often prevents loss of the graft.

Graft infection

Infections can occur early or late. They are a medical emergency and can lead to loss of the graft, or even of the eye. Good hygiene and strict adherence to the post-operative treatment are essential to prevent this complication.

Ocular hypertension

An increase in intraocular pressure may result from corticosteroid treatment or inflammation. If it is not controlled, it can damage the optic nerve and cause glaucoma.

Astigmatism

Corneal distortion can appear after the transplant, especially after full-thickness (penetrating) grafts. It may require additional optical or surgical correction.

Urrets-Zavalia syndrome

This is a rare complication characterized by irreversible dilation of the pupil (mydriasis), often after a DALK. It may be linked to iris ischemia or to the use of mydriatic drops during surgery.

Cornea guttata and Fuchs dystrophy

Fuchs dystrophy is a degenerative disease of the cornea, characterized by a progressive loss of endothelial cells. It leads to corneal edema and reduced vision. DMEK is now the gold-standard treatment for this condition, offering excellent visual results.

What is keratoconus?

Keratoconus is a progressive, non-inflammatory disease of the cornea in which it takes on an irregular cone shape. It usually begins in adolescence and can progress to severe vision loss. If conservative treatments (rigid lenses, cross-linking) fail, a corneal transplant, usually of the DALK type, may be indicated.