Cornea Transplantation

About The Cornea

The cornea is the transparent 'front window' of the eye. The cornea is important because it is the main focusing structure of the eye and so any change in its shape or transparency will reduce vision.

What Is Cornea Transplantation?

Many diseases can damage the cornea to such an extent that the only effective treatment is to replace it with a new, normal cornea. This may occur in keratoconus, Fuchs' endothelial dystrophy, after cataract surgery, after Herpes virus cornea infection etc - these diseases are discussed in other chapters of the eyesite.

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 and are of the highest quality. For example, everything possible is done to exclude corneas from donors with transmissable diseases.

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 disc of tissue from the centre of the patient’s own cornea and its replacement by the transplant. The surgery can be combined with cataract extraction if necessary. Like all surgery, cornea transplantation entails some risk and should only be done when absolutely necessary.

Full thickness or penetrating transplantation. The full thickness of the patient’s diseased cornea from the outer to the inner surface is replaced. This is the oldest method.

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

in health, the cornea is perfectly clear

this technique is suitable when disease extends through the full thickness of the cornea

a circular cut is made into the diseased cornea

the diseased cornea is removed

a healthy cornea is transplanted into the space created by removal of the patient’s diseased cornea

the cornea transplant is held in place with ultra-fine sutures.
These are not visible to the naked eye.
The transplant bonds slowly to the patient’s cornea and the sutures are then removed

I performed this full thickness cornea transplant
for a patient with keratoconus
(The patient is looking slightly sideways)

There are 16 minute black sutures
holding the transplant (arrow) in place

The sutures are removed when the transplant has healed

Full thickness cornea transplant aftercare

Eyedrops containing steroid and antibiotic are needed after the operation for a variable period, generally about 6 months. Unlike other transplants eg kidney or heart, tablets to prevent rejection are not usually 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 months or longer. 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 because of 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 vision correction surgery (refractive surgery) after transplantation to reduce dependence on contact lenses. Please see the eyesite on vision correction.

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 uneveness 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 often 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 thickness or deep anterior lamellar transplantation. This method saves some of the patient’s own cornea and only replaces the outer layers. This greatly reduces the chance of some complications such as rejection. It is more technically difficult than penetrating transplantation. However it is ideal in some circumstances, for example keratoconus.

N.B. These illustrations of partial thickness transplantation of the front/anterior/stromal region of the cornea (deep anterior lamellar keratoplasty) should be understood as a general guide to the surgery, rather than an exact description.

in health, the cornea is perfectly clear

diseased corneas may be scarred and/or abnormally shaped

the surgeon will remove the diseased front/anterior/stromal region of the cornea

air is injected into the cornea to separate the abnormal front/anterior/stromal region from the normal endothelial (back/innermost/posterior) region

the abnormal front/anterior/stromal region is then completely removed

a healthy cornea is transplanted into the patient’s cornea to replace the diseased front/anterior/stromal region.
The cornea transplant consists only of the front/anterior/stromal region of healthy cornea
– the endothelial (back/posterior/innermost) region has been removed so that the new cornea fits exactly into the patient

the cornea transplant is secured with ultra-fine sutures

Partial thickness or selective corneal endothelial transplantation.

This method is a major step forward in cornea transplantation. Only the innermost layer of the cornea, called the ‘endothelium’, is removed from the patient’s cornea and replaced. The replacement, from the donor cornea, also consists only of endothelium. The great advantage of this method is that the donor material is not sutured (stitched) into place. Rather it self-adheres. This means that the patient typically has very much less astigmatism after the operation than using the older technique of penetrating transplantation. This is important because patients may not need to wear a contact lens in order to see properly after the operation. This operation is particularly appropriate for diseases in which only the cornea endothelium is diseased, but the other layers of the cornea are healthy, eg: pseudophakic bullous kerathopathy or Fuchs.

I was one of the first eye surgeons in the United Kingdom to perform this exciting new form of cornea transplantation.

N.B. These illustrations of selective replacement of the endothelial (back/innermost/posterior) region of the cornea should be understood as a general guide to the surgery, rather than an exact description.

in health, the cornea is perfectly clear

the endothelial (back/innermost/posterior) region of this cornea is diseased eg: in Fuchs’ dystrophy

the diseased endothelial (back/innermost/posterior) region is removed leaving the normal front (anterior) region in place

a normal cornea will be transplanted into the patient. (a) the healthy endothelial (back/innermost/posterior) region is
removed to match the diseased region that has been removed from the patient’s cornea.
The transplant is (b) folded and (c) inserted into the patient’s eye via a minute incision in the cornea

after insertion, the transplant is unfolded

air is injected to position the transplant against the patient’s cornea.
Once contact is achieved, the transplant will adhere permanently, without requiring sutures

post-operative appearance of cornea transplant (blue region).
Sutures are not required to hold the transplant in place

An opaque cornea prior to selective corneal endothelial transplantation.

A patient with Fuchs’ after selective endothelial transplantation.
The cornea is crystal clear.

For more information read Fuchs or master class on selective corneal endothelial transplantation