Corneal transplant remains to be an effective way to restore vision of a diseased or scarred corneal.

 

BY: Eleanor Yap

 

Corneal transplant is said to be an effective procedure to restore vision by replacing a diseased or scarred corneal with a healthy-donated corneal tissue. The Singapore National Eye Centre (SNEC) has performed about 250 to 300 corneal transplants each year, and last year alone, 277 corneal transplants were performed. SNEC does 80 percent of corneal transplants in Singapore.

Agelessonline talks to Dr Lim Li, senior consultant and head (Clinical Service and Education), Cornea Service, SNEC, about the different types of corneal transplants and how to protect one’s eyes:

 

What are some conditions that necessitate a corneal transplant?

A cornea transplant replaces a diseased or scarred cornea with a donor cornea. A cornea transplant is an effective means of restoring vision in cases of corneal diseases, injuries, infections and age-related corneal degeneration.

There are several corneal diseases that require corneal transplantation. The cornea, which is the transparent front part of the eye, is made up of three main layers: Epithelium (surface layer), stroma (middle layer) and endothelium (inner layer), and diseases affecting any of these layers may lead to loss of transparency of the cornea thereby necessitating a transplant. The commonest indication for corneal transplantation is bullous keratopathy, where the cornea swells up and becomes opaque due to a failure of the endothelial layer.

Other common indications for corneal transplantation include corneal scarring usually from a previous corneal infection, corneal infection (keratitis) and fuch’s endothelial dystrophy which is a weakness of the endothelial layer which leads to early failure and bullous keratopathy. The conditions that are more common in the ageing population are bullous keratopathy and fuch’s endothelial dystrophy.

 

Can you go over the procedure of a corneal transplant? How long is the surgery? How long do they get back to normal activities? What patients will be rejected from a corneal transplant?

A corneal transplant is a microsurgical operation performed by a trained corneal transplant eye surgeon. There are several types of corneal transplant procedures that are performed in SNEC. The standard corneal transplantation technique is a Penetrating Keratoplasty (PK) or a full-thickness corneal grafting procedure. During PK, the central 7mm to 8mm portion of the damaged or cloudy cornea is removed and a clear and healthy donor cornea is sutured in its place with very fine microsurgical nylon sutures.

SNEC also performs newer and more advanced forms of corneal transplant called Lamellar Keratoplasty (LK), or partial thickness corneal grafting where only the diseased portions of the cornea are removed and replaced, preserving more healthy corneal tissues. These procedures greatly reduce the risk of corneal graft rejection which is a significant cause of graft failure in corneal transplants. When only the anterior (front) layers of the cornea are replaced, the procedure is called Anterior Lamellar Keratoplasty (ALK), and when most of the anterior layers are removed, the procedure is termed Deep Anterior Lamellar Keratoplasty (DALK). These are more surgically challenging operations that preserve the deepest layer of the cornea. About 30 percent of corneal transplants at SNEC are performed with ALK or DALK procedures. SNEC today is one of few transplant centres in the world that offers these new advanced LK techniques to corneal transplant patients.

When only the diseased posterior or back layers of the cornea are replaced, the procedure is called Endothelial Keratoplasty (EK or DSAEK – Descemets Stripping Automated Endothelial Keratoplasty). SNEC is the regional referral centre in Asia for EK surgery where half of all corneal transplants at SNEC are EKs. EK is probably the most significant advance in corneal transplantation today, because it is a new form of suture-less, keyhole corneal transplant technique. Only the innermost thin layer of the cornea is replaced, and this is done through a small (4mm to 5mm) incision at the side of the cornea, which means that most of the patient’s cornea is no longer removed, no sutures on the cornea are now needed, and the eye is much stronger as compared to PK surgery. No sutures also means much faster visual recovery and EK patients also have better vision because they have much less astigmatism and other refractive errors.

 

What are the risks of a corneal transplant?

Over the past 20 years, the number of corneal transplants performed has increased steadily from 50+ cases a year 20 years ago to 300+ cases a year currently. Due to the successful corneal procurement programme implemented by the Singapore Eye Bank, there are now more donor corneas available, and more transplantation procedures can now be performed.

The success rate varies according to the type of procedure. PK graft and EK graft survival rate are about 90 percent at one year. The graft survival for PK at five years drops to about 60 percent. The advantage of EK over PK is better vision and corneal strength, and less endothelial cell loss over time. ALK/DALK grafts survive very well with a much lower rejection rate over time.

Visual recovery is gradual and may take several months for PK/ALK/DALK. EK, being a keyhole transplant technique, has a faster recovery with significant visual improvement at about one month.

Unlike other forms of organ transplants, corneal transplants may be performed several times if previous attempts fail. However, the success rate of repeat transplants may be lower than a first-time graft and anti-rejection tablets may be needed to prevent rejection in these cases.

 

How old is the oldest patient you have treated been and what condition did he or she have? Was it a success?

The oldest patient I have performed a corneal transplant on is 82 years old and following the transplant she is enjoying clear vision today.

 

Out of the more than 250 corneal transplants, how many have been done for patients 50 and above and how many have been a success? What are some reasons for the transplant not being a success?

About 52 percent of our corneal transplant patients are over 60 years old. The incidence of graft survival differs according to the indication for corneal transplantation and type of corneal transplantation performed. For example, graft survival for penetrating keratoplasty (full thickness corneal graft) varies from 100 percent to 50 percent at five years depending on the indication for transplantation.

The commonest reason why a corneal graft fails is allograft rejection, where the graft is rejected and becomes swollen and opacified resulting in poor vision.

 

Under what circumstances does a corneal infection warrant a corneal transplant? What are the different types of infection?

Cornea infection, or keratitis can be bacterial, fungal, viral or amoebic in nature. Severe infective corneal ulcers which do not respond to medical treatment may require urgent corneal transplantation to salvage the eye. Other corneal ulcers respond to medical treatment with significant central corneal scarring affecting the vision and may require elective corneal transplantation to restore vision.

 

What is the cause of eye infection?

Keratitis is a serious eye infection of the cornea. It may develop very quickly and can lead to ulceration, scarring and loss of vision. Exposure to viral or bacterial infections can cause eyes to become red, swollen and watery. One of the common causes of corneal infection is contact lens wear.

 

How can one maintain good corneal health?

Prevention

Eye infections usually occur because of contact with viruses or bacteria. To prevent these harmful agents from entering your eye, follow the guidelines below:

• Wash your hands before and after touching your eyes or face.
• Avoid sharing eye make-up and change eye make-up every six months.
• If you have an existing eye infection, avoid using any eye make-up or wearing contact lenses until the infection clears up.
• Practise good contact lens care and never share contact lens equipment, containers, or solutions.
• Do not share towels, linens, pillows, or handkerchiefs.
• Wear eye protection when in the sun, wind, heat, or cold to prevent eye irritation.
• Wear safety glasses when working with chemicals.
• Avoid exposing your eyes to contaminated water.

Treatment

You should see your eye doctor to determine the cause of your eye infection and get advice on the best course of treatment.

In some cases of conjunctivitis, non-steroidal anti-inflammatory medications and antihistamines may be prescribed. Some patients with persistent allergic conjunctivitis may also require topical steroid drops.

Eye infection cases need treatment with antibiotic eyedrops, especially when non-viral causes are involved. Cornea infections or ulcers may even require hospitalisation.

 

*** NOTE: When asked about the cost, the writer was told the starting cost for a cornea transplant can only be advised upon consultation with an eye specialist and the cost is covered by Medisave.

(** PHOTO CREDIT: Singapore National Eye Centre)

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