About The Cornea

The cornea is the transparent 'front window' of the eye and is also an important focusing structure: any change in its shape or transparency will reduce vision.

What Is Cornea Transplantation?

Some diseases damage the cornea so badly that the only treatment is to replace it with a new, normal cornea. Examples are keratoconus and Fuchs.

Cornea transplantation is the replacement of the patients' own cornea with one donated by a deceased person. It is the same in principal as a kidney or heart transplant although cornea transplantation is a 'smaller' operation because it is much less stressful for the body and it is not necessary to take tablets to prevent the new cornea rejecting.

The donor corneas are supplied by United Kingdom Transplant located in Bristol, England or equivalent centres in the USA and are of the highest quality. For example, corneas from donors with transmissable diseases are excluded.

You may come across the term ‘keratoplasty’ which means the same as cornea transplantation.

Different Types Of Cornea Transplantation

There are several types of cornea transplantation. They generally involve the removal of a circular area from the centre of the patient’s own cornea and its replacement by the transplant. Cataract surgery may be done at the same time if necessary. Like all operations, cornea transplantation entails some risk and should only be done when absolutely necessary.

The centre of the patient’s own cornea is completely removed and replaced by a transplant which is sutured (stitched) into place.

(These illustrations of full thickness transplantation of the cornea (‘penetrating keratoplasty’) should be taken as a general guide to the surgery, rather than an exact description)

Full thickness cornea transplant aftercare

Eyedrops containing steroid and antibiotic are used after the operation for a variable period, generally about 9 months. Unlike other transplants eg kidney or heart, tablets to prevent rejection are not needed. However patients with cornea disease caused by herpes virus infection may need long term medication with Zovirax antiviral tablets to prevent recurrence of the virus on the transplant.

Fairly frequent review in outpatients is required during the first year after the surgery.

The sutures that hold the transplant in place are non-dissolving and need to be removed after 9-12 months. This is not painful and does not need an anaesthetic. It is done in outpatients.

Vision recovery after surgery is usually very slow and can take 9-18 months. It is normally necessary to wear a contact lens to obtain good vision after transplantation. It is not normally possible to see clearly after transplantation with glasses or 'naked eye'. This is due to astigmatism which is discussed below. The contact lens needs to be a rigid gas permeable (hard) type. Soft lenses do not provide adequate vision.

It is sometimes possible to have refractive surgery after transplantation to reduce dependence on contact lenses. Please see the eyesite on refractive surgery.

Full thickness cornea transplant potential complications

In expert hands the outcome of cornea transplantation is usually good. However it is important to be aware of potential complications which include -

Astigmatism: This is caused by unevenness of the shape of the new cornea after it has healed and is found in virtually every transplant. Astigmatism is not dangerous but does reduce vision. The solution is to wear a rigid gas permeable (hard) contact lens which neutralises astigmatism.

Rejection: The body may reject the new cornea. The chance of this happening depends on features specific to each patient. Rejection causes vision to become cloudy and the eye may be red and sometimes sore. It is usually possible to reverse rejection by prompt administration of steroid eyedrops or injections.

Infection: Various bacteria may infect the transplant requiring intensive antibiotic eye drops. Cornea disease caused by herpes virus may reactivate on the transplant causing scarring.

Wearing Out: A cornea transplant can simply wear out because its cells age more quickly than those of a normal cornea. A new transplant is required to replace it.

Partial cornea transplantation (‘deep anterior lamellar keratoplasty’)

This method saves some of the patient’s own cornea and only replaces the outer layer. This is ideal in keratoconus because in many cases it is only the outer layer of the cornea (called the ‘stroma’) that is abnormal whilst the inner layer (called the ‘endothelium’) is healthy. Preserving the patient’s healthy endothelium is important as it greatly reduces the risk of transplant rejection.

I always perform partial or 'deep anterior lamellar keratoplasty' when it is possible to do so. However if the keratoconus is too advanced, for example the cornea is severely scarred, this surgery may not be possible and full thickness or penetrating ‘keratoplasty’ is done instead.

(These illustrations of partial cornea transplantation ('deep anterior lamellar keratoplasty’) should be understood as a general guide to the surgery, rather than an exact description.)

Partial cornea transplantation (‘deep selective automated endothelial keratoplasty' - DSAEK)

Daily Mail on Fuchs’

This is a major advance in cornea transplantation as it saves some of the patient’s own cornea. Only the innermost layer (called the ‘endothelium’) is replaced and the outer layer (called the ‘stroma’) is unchanged. The great advantage of this method is that the donor self-adheres and is not sutured (stitched) into place. There is no astigmatism, unlike the older technique of full thickness transplantation, so contact lenses are not needed after surgery. This operation is for diseases in which only the endothelium is diseased eg Fuchs’ I was the first surgeon to perform the new operation in the United Kingdom.The article below, originally written for optometrists, describes it in more detail.

New frontiers in cornea transplantation : selective transplantation of the endothelium via a no-suture, keyhole incision

The cornea is the clear ‘front window’ of the eye. It may be damaged by disease processes such as Fuchs’ corneal endothelial dystrophy or inadvertently during cataract surgery. Damage causes the cornea to become opaque and the eye blind.

The treatment for severe cornea disease is cornea transplantation – the patient’s cloudy cornea is removed and replaced by a clear cornea obtained from a deceased person, a process similar to kidney and heart transplantation. For decades the technique used has been ‘full thickness’ cornea transplantation. This entails the removal of the entire cornea and its replacement by a transplant. Whilst traditional, full thickness cornea transplantation may successfully restore vision, it may also cause complications. These include severe astigmatism (distortion of the focus of the eye, necessitating the wearing of hard contact lenses after the operation), glaucoma (raised pressure inside the eye) and rejection of the transplant (necessitating another operation to replace it). Full thickness cornea transplantation is also undesirable because it requires virtually the entire front of the patients’ eye to be removed and replaced by the transplant – such large scale surgery may be very traumatic to this delicate organ.

Recently, a remarkable new treatment for cornea disease has become available. This is a revolutionary method of cornea transplantation called ‘selective endothelial transplantation’. The ‘endothelium’ is the layer of the cornea which is on the inside of the eye. Many cornea diseases damage only the endothelial layer, the other regions of the cornea remaining clear. Fuchs’ corneal endothelial dystrophy and damage occurring during cataract surgery are examples. Using the new technique only the diseased endothelium is replaced leaving the remainder of the cornea, which is healthy, in place.

Selective corneal endothelial transplantation is performed through a minute incision on the surface of the eye, only about 4 mm wide. This is approximately the same size as the incision made during cataract surgery. The diseased inner layer is removed through this tiny incision. A transplant composed of healthy corneal endothelium is inserted by gently folding it so that it can enter through the incision. Once inside the eye it is carefully manipulated into position and will miraculously adhere to the patient’s own cornea without sutures!

The new technique is greatly superior to traditional, full thickness cornea transplantation. The tiny incision causes much less trauma to the delicate eye. Disabling post-operative astigmatism is eliminated altogether, no sutures are required and recovery after the operation is much faster.

Case study : A 78 year old lady suffers from Fuchs’ corneal endothelial dystrophy. Her right eye received a full thickness cornea transplant several years previously. Sixteen sutures were required to secure the transplant in place. It was 18 months before healing was complete. She can only see from her right eye whilst wearing a hard contact lens which must be inserted every morning and removed before bed. By contrast her left eye received a selective corneal endothelial transplant a few months ago. Recovery was complete after three months, no sutures were needed and she sees well from her left eye without needing to wear a contact lens.