Corneal Transplant

Corneal Transplants:

A corneal transplant is defined as the removal of a portion of a diseased cornea and replacing it with a new section from a donor cornea.

What is the cornea?

The cornea is a transparent tissue that is dome-shaped covering the front of each eye. It is the “windscreen” of the eye.
The cornea is made up of five layers. It normally does not contain any blood vessel and is a clear and smooth surface. It is important that the cornea remains clear to allow light to pass through the eye.

Who needs a corneal transplant?

A corneal transplant is required for:

  • Scarring of the cornea from infection, disease or trauma
  • Warping, distortion and thinning of cornea from conditions such as keratoconus where the cornea.
  • Hereditary corneal conditions which reduce corneal clarity such as Fuchs’ Endothelial Dystrophy.

What is Fuchs’ endothelial corneal dystrophy?

Fuchs’ dystrophy is a degenerative hereditary disease that affects the innermost layer of cells in the cornea known as the endothelium. The endothelium is the layer of cells responsible for maintaining levels of fluid in the cornea. The purpose of the endothelium is to maintain a clear cornea for optimal vision by pumping out excess fluid which can cause corneal swelling.

It is usually an inherited condition although as it presents later in life, often people are unaware that it has affected other family members.

As Fuchs’ dystrophy progresses, swelling in the cornea can lead to blisters at the front of the cornea, known as bullous keratopathy, which can be very painful.

Symptoms:

  • Blurred vision on waking as a result of fluid that has collected in the cornea whilst sleeping. As the excess fluid evaporates during the day the vision becomes clearer and the swelling reduces;
  • Sensitivity to light;
  • Fluctuations in vision;
  • The appearance of haloes around lights; and
  • A gritty or rough sensation in the eye, with significant pain in more advanced cases.

Treatment:

  • The use of hypertonic saline to help remove excess fluid build up.
  • Glaucoma eye drops if intraocular pressures are high to stop further damage to the corneal endothelium.
  • Corneal transplantation, of which there are several different types.

Types of corneal transplant:

Penetrating Keratoplasty(PK) (full thickness)

A full thickness corneal transplantation is where the damaged cornea is removed and a new donor cornea is sutured in place using very fine stitches.

The surgery may be performed under local anaesthesia with sedation, or very occasionally under general anaesthesia. It normally takes 60 – 90 minutes.

Cataract surgery may be performed at the same time if required.

Recovery to stable vision normally takes 18 months or longer.

DSEK (Descemets’ Stripping Endothelial Keratoplasty)

The diseased endothelial layer of the cornea is replaced rather that the full thickness of the cornea, such as in the case of Fuchs’ Endothelial Dystrophy. This surgery is called “Descemets’ Stripping Endothelial Keratoplasty” or “DSEK”. The goal is to remove the minimum amount of corneal tissue and replace it with healthy donor tissue to resolve the oedema (or swelling) of the cornea and restore vision.

The operation is performed under assisted local anaesthesia, this means that whilst patients are awake they are given sedation and are generally unaware of the operation going on around them.

A single small incision, similar to that used for cataract surgery is made, and the diseased endothelial layer of the cornea is removed. The healthy donor endothelium and back layer of the donor cornea is then placed through the incision. The initial incision is then closed with several stitches and the procedure is completed. A small air bubble is left inside the eye to help position the donor transplant tissue. Following the surgery the facing the ceiling. The air bubble is simply absorbed by the body and disappears over about 5 days.

Advantages of this procedure include:

  • Fewer sutures which causes smaller changes in astigmatism less need for strong spectacles   following surgery;
  • A stronger eye, as the incision into the eye is much smaller than with a penetrating keratoplasty;
  • A lower risk of rejection as less corneal donor tissue has been used.
  • Recovery in vision is quicker, approximately 3 – 6 months.

As with all transplant surgery, there is a risk of rejection or failure of the transplant in both the early and late stages after the surgery. If this occurs, repeat grafting either with a repeat DSEK transplantation procedure or repeat full thickness corneal transplant may be necessary.

DMEK (Descemets Membrane Endothelial Keratoplasty)

This is the newest type of partial thickness corneal transplant. Only the enothelial cells and the membrane holding the endothelial cells in place are transplanted, which is only about 20 micrometers thick.

It is a technique using small incision. The patient's original cornea is left mostly intact, it replaced only the damaged corneal endothelial cells which are on a membrane which is

The advantages include:

  • Minimally invasive
  • An even more rapid visual recovery
  • A better chance of attaining 6/6 or 20/20 vision than with DSEK or PK surgery.

DMEK surgery is not suitable for all cases of endothelial disease. Because of the delicate nature of the surgery, occasionally multiple procedures to attach the donor cornea may be required.