What is the Cornea?
The cornea is the transparent front layer of the eye that covers the coloured iris and round pupil. An important function of the cornea is to focus light rays onto the retina. If the cornea becomes cloudy (opaque) or distorted due to disease or injury, a corneal graft may be required to restore clarity of vision.
What Conditions may require a Corneal Graft?
Keratoconus: Keratoconus is a condition where there is progressive thinning and steepening of the central cornea resulting in decreased vision. This vision loss can initially be corrected by spectacles. Rigid contact lenses are the usual treatment option but in approximately 20% of cases, corneal grafts are required.
Bullous Keratopathy: This occurs when the endothelial cells on the back of the cornea are damaged. Endothelial cells are responsible for pumping fluid from the cornea. If these cells are not working, the cornea can become “waterlogged”. This causes the vision to deteriorate and the eye can feel painful.
Corneal Scarring: Scarring can be caused by infection, inflammation or trauma, such as corneal lacerations or penetrating eye injuries. The light cannot travel through the cornea normally and vision is affected.
Hereditary Corneal Disorders: Such as Fuchs’ dystrophy can lead to swelling or cloudiness of the cornea, causing decreased vision. The disorder involves the endothelium and if it is unhealthy, the cornea loses its transparency.
Failed Previous Graft: Failure is usually secondary to rejection leading to endothelial damage and bullous keratopathy.
Penetrating Keratoplasty (PK):
In this procedure a full-thickness button of diseased cornea is removed and a full thickness replacement donor corneal button is sutured in place. The procedure takes approximately 45 – 60 minutes.
Deep Anterior Lamellar Keratoplasty (DALK):
Patients with keratoconus and corneal scars would benefit from this operation. In this procedure only the front part of the cornea is removed, leaving the patient’s own back part of the cornea (Descemet’s membrane and endothelium) intact. A donor corneal button with the back part removed is then sutured in place.
Descemet stripping automated endothelial keratoplasty (DSAEK)
Patients with corneal oedema, corneal decompensation or bullous keratopathy would benefit from this procedure. The operation involves removal of the patient’s own Descemet’s membrane/endothelium and transplantation of donor healthy Descemet’s membrane and endothelium. This procedure minimises the need for sutures and allows for more rapid visual recovery.
Descemet’s membrane Endothelial Keratoplasty (DMEK)
This procedure is similar to DSAEK, but involves transplantation of a thinner layer of donor cornea. This can lead to better vision, less rejection and faster recovery compared to DSAEK. However it has a higher failure rate and may require a second procedure if there is graft failure.
Corneal grafting can be a day procedure or you may need to stay overnight. It can be performed under local or general anaesthesia. You may experience mild pain after the procedure. Your vision will be blurry for a few weeks after surgery, and you may not have clear vision for several months. You will need to use eye drops for a least 6 months after the surgery, often longer. It is recommended that you take at least 2 weeks off work and avoid heavy lifting and exercise for one month. You will need to return for follow-up visits at least 8 – 10 times in the first year.
A new glasses prescription can be worn when the graft is clear and the refraction is stable. In most people this occurs in approximately 3-6 months. Contact lenses cannot be worn until the sutures have been removed. Vision and refraction may change after the sutures have been removed, requiring a new glasses prescription or contact lens. Over 70% of people are able to see well with glasses. A small percentage of patients require rigid contact lens to see well.
The most common complication following corneal grafting is rejection, however approximately 80% of rejections can be reversed with drops. There is also a risk of bleeding, infection, glaucoma, cataracts, graft rupture and graft failure.
As your new cornea will always be weaker than your own cornea, it is recommended that you do not play contact sports. You will need to be in regular contact with your ophthalmologist as there will always a risk of rejection.