Corneal transplantation for Keratoconus

Corneal transplantation for keratoconus

Corneal transplantation may be necessary for those with severe forms of keratoconus but it is important to be aware that this is not a simple and quick fix for the problem. The procedure involves removal of the distorted central part of the cornea and replacement with an appropriately-sized piece of cornea from a donor (someone who has died). This is a proper transplant procedure and synthetic grafts are not available yet for this problem.

Corneal transplants for keratoconus are mostly done as what are called Deep Anterior Lamellar Keratoplasty (DALK) procedures. This leaves the innermost layers of the recipient’s cornea (Descemet’s membrane and corneal endothelium) in place and replaces only the front, distorted, part of the cornea. This potentially reduces the chance of rejection of the graft and may have other advantages over replacing the entire thickness of the cornea (Penetrating Keratoplasty, PK) though there is not a great deal of very long term information about this.  It is not always technically possible to do the transplant as a DALK procedure and there are some potential complications specific to that method, including non adherence of the layers of the cornea or wrinkling of the thin recipient layer that can affect vision.

How is a corneal transplant performed?

The surgical procedure is usually done under general anaesthetic with an overnight stay in hospital. It is relatively straightforward but the healing afterwards is prolonged. The graft is secured with extremely fine nylon sutures that need to stay in place for 12 to 18 months. Recovery of vision after the graft is very variable. Some people may have quite good unaided vision after a month or so. For the majority of people, though, it takes much longer for vision to improve and it may not be good until the stitches have been removed (i.e. 18 months down the track).

One in five people will require another operation after the stitches have been taken out to adjust the shape of the graft to allow contact lens fitting or spectacle correction. Many will need laser treatment as well to get good vision.

Overall, it may take 2-3 years to get to the stage where vision is as good as it can be. It is possible to reduce the need for glasses or contact lenses after the graft by doing laser treatment but this has to wait until everything has stabilised after the sutures have been removed.

It is very important to realise that having a corneal transplant will not make your vision normal. Many people who have a corneal graft will still need to wear quite thick glasses or contact lenses to have good vision.

Potential risks and problems associated with a corneal transplant

There is a risk of rejection of the graft. This may start to occur in up to 25% of grafts but is usually reversible with treatment. If the graft rejects completely it will go cloudy and will have to be repeated. The chance of a second graft surviving in that case is less than the first. There is a greater chance of the graft rejecting for those people who have associated allergic problems. Those who do have allergy issues are much more likely to have problems overall after corneal transplantation – including surface problems, uneven healing, suture reactions and pressure problems.

Corneal grafts do not last forever. They may last 25-30 years in very good circumstances but will then need to be repeated as the graft gradually becomes hazy or the keratoconus process affects the remaining cornea and distorts the graft itself out of shape.

Overall, 95% of grafts survive for 5 years and 90% for 10 years. That means that 1 in 20 will fail (mostly due to rejection) over 5 years.

Anti-rejection drugs are not usually used for corneal transplants as they have multiple potentially severe side effects and the survival rate of the transplants is very good without them. Drugs are used in the form of eyedrops and may need to be used indefinitely.

Rarely a graft will not work right from the start and will need to be replaced straight away.

The donor corneas are screened for the presence of potentially transmissible diseases but despite this there is a very small risk of developing a disease from the graft itself.

Experience Life Clearly

Dr. Steven Wiffen is a consultant ophthalmologist subspecialising in cornea, cataract, laser and refractive surgery.