What is a corneal transplant?
The cornea is the dome-shaped window that forms the front surface of the eye. It is made up of several layers, all of which are transparent. Diseases of the cornea may affect one or more of these layers.
Corneal transplant surgery, also known as corneal graft surgery and keratoplasty, replaces an abnormal cornea with a cornea from a donor eye in order to restore vision.
Who needs a corneal transplant?
Many people with a cloudy cornea from scarring after infection or injury will benefit from corneal transplant surgery. Some inherited or degenerative conditions, like Fuch’s endothelial dystrophy, may lead to swelling of the cornea, which requires corneal transplant surgery when it affects the vision or causes pain. In keratoconus the cornea becomes thinned and distorted, resulting in blurring of vision. In about 15% of cases, when other treatments such as contact lenses no longer help, corneal transplantation is necessary.
Unlike most other organ transplants, if a corneal transplant fails it can be repeated, although the success rate of repeat transplants may be lower than first time transplants.
How is corneal transplant surgery performed?
Corneal transplant surgery may be performed under general or local anaesthetic. It generally takes between one and two hours and is day surgery, not requiring an overnight hospital stay.
There are several types of corneal transplants performed by Eye Doctors. In about half of corneal transplant surgery all corneal layers are affected, requiring a standard, full thickness transplant or ‘penetrating keratoplasty’ (PK). This includes surgery for some corneal scars and some keratoconus, which is the most common reason for corneal transplant surgery in New Zealand. The central 7-8mm of the damaged cornea is removed and replaced with a similar sized piece of clear donor cornea, which is stitched in place with fine nylon microsutures.
In other cases, particularly the less advanced cases of keratoconus, a partial thickness ‘deep anterior lamellar keratoplasty’ (DALK) may be suitable. In this surgery the innermost corneal layer, or endothelium, is healthy, so is not replaced. This reduces the risk of corneal transplant rejection and failure in the long term.
Other corneal disorders only require replacement of the innermost corneal layer, or endothelium. In Fuchs’ dystrophy and bullous keratopathy only this thin layer needs to be replaced, in a procedure known as ‘descemets stripping automated endothelial keratoplasty’ (DSAEK). This is done through a small keyhole incision at the edge of the cornea and has the advantages of a faster healing time and no/minimal stitches on the eye.
Eye Doctors are experienced in medical treatment of corneal diseases and in the latest surgical techniques for corneal transplantation, including partial thickness corneal transplantation. Our corneal surgeon can discuss the different types of corneal transplant with you and which type of surgery is most suitable.
Is corneal transplant surgery safe?
Corneal transplantation is quite a major surgery for the eye and should not be undertaken lightly. The healing period can be over a year for full-thickness corneal transplant and while the final vision can be as good as 20/20 (6/6), this is certainly not guaranteed.
Significant complications during the surgery are rare, but there are some potentially serious risks, such as transplant rejection, which can lead to transplant failure if not treated promptly. Our corneal surgeon can advise you of the pros and cons of corneal transplant surgery.
What is keratoconus?
The cornea is the transparent dome-shaped window on the surface of the eye, overlying the coloured iris. Its smooth round surface is important for maintaining clear vision. In keratoconus the cornea becomes thin and distorted, eventually protruding forwards in a cone-like shape. It typically affects both eyes, but can often be quite asymmetric.
Why does keratoconus develop?
The causes of keratoconus are not very well understood. However there is a genetic tendency, so it can sometimes run in families. There is also an association with allergies and most people with keratoconus have itchy eyes and rub their eyes to some degree. Over several years the pressure on the eye from rubbing may contribute to distortion of the cornea.
Who gets keratoconus?