The Royal Shrewsbury Hospital is leading the field when it comes to pioneering eye surgery and is the only NHS hospital offering patients the latest revolutionary procedure for corneal transplants.
This new operation reduces recovery time and increases the quality of a patient’s vision compared with older operations. The operation is called Descemet’s Membrane Endothelial Keratoplasty (DMEK) and was pioneered some five years ago by Dutch researcher Dr Gerrit Melles, from the Netherlands Institute for Innovative Ocular Surgery.
Mr Ewan Craig, Consultant Ophthalmologist and Lead Clinician at The Shrewsbury and Telford Hospital NHS Trust, has been using the technique since July 2008 and has successfully treated more than 20 patients. He is currently the only surgeon in the UK providing this procedure.
The cornea is the clear window that lets light into the eye and is responsible for most of its focussing power. It protects the eye from infection and physical damage but is just half a millimetre thick. The cornea is made up of five layers and is mostly made of water and collagen. The inside layer is a sheet of cells called endothelial cells. These cells act as tiny pumps removing excess water from the cornea. Without the endothelial cells the cornea swells and becomes cloudy, much as the skin on your fingers goes white and swollen after too long in the bath.
In the disease known as Fuch’s Corneal Dystrophy (FCD) these endothelial cells die off. This causes a build up of excess fluid in the cornea, which then becomes cloudy resulting in blurred vision. In later stages the water-logging can increase and cause small blisters to form on the surface of the cornea. These blisters can burst causing pain and scarring the cornea, which reduces vision even more. FCD cannot currently be cured, but transplanting a healthy cornea from a donor can cure the problems it causes.
The first successful corneal transplant was carried out in 1906 by cutting a circular hole in the patient’s cornea, and repairing it by stitching in a circular piece cut from a donor cornea. This operation, with minor improvements, is still carried out over 100 years later. Although this operation improves vision it has significant drawbacks. Slight differences in the shape of the patient and the donor corneas and minor unevenness of the stitches can cause distortion of the donor cornea, resulting in poor focus, which has to be corrected with strong glasses or a contact lens. The cornea is very slow to heal, meaning that the stitches have to be left in for a year or two and it typically takes 18-24 months before the eye has reached its best vision. Problems with broken stitches can result in infection or rejection of the transplanted cornea and a relatively weak wound leaves the eye vulnerable to the effect of injury in the long term.
During the past 10 years surgeons have tried to improve corneal transplants by using partial thickness transplants in which thinner and thinner discs of cornea are used and various techniques have evolved. Having used earlier partial thickness techniques for corneal transplantation since 2002 (including the confusingly named DSEK), Ewan Craig has found the latest technique known as DMEK to be so superior in outcome that it is now his first choice operation whenever the patient is suitable.
The DMEK operation appears to have taken this reduction of transplanted corneal material to its limit. Only the endothelial cells and their supporting structure, the Descemet’s Membrane (which is only a tenth of the thickness of a human hair), are transplanted. This minimises the disruption caused by the operation to the eye and greatly reduces the time for recovery of vision.
When Dr Gerrit Melles, the world-leading pioneer of lamellar corneal surgery from Rotterdam demonstrated a patient on whom he had performed the newest technique of Descemet’s Membrane Endothelial Keratoplasty (DMEK) to UK Corneal surgeons in 2008 Ewan Craig was astounded at the result. A trip to Rotterdam six weeks later to see Dr Melles operate and to view the results of yet more operations convinced him that this new operation was another significant step forward.
Ewan Craig performed his first DMEK in July 2008. One week later the patient could see well enough with the operated eye to drive and could read the very bottom line on the test chart (6/5) within three months of the operation.
Since then DMEK has been his first choice procedure for all suitable patients. The visual outcomes of his patients having DMEK have proved to be significantly better than those who had the older DSEK operation. The results of DMEK have been particularly good in patients with Fuch’s Corneal Endothelial Dystrophy.
In the DMEK procedure the Descemet’s Membrane along with the healthy endothelial cells is carefully peeled from the donor cornea. The equivalent, diseased piece of tissue is removed from the patient’s eye. The harvested tissue from the donor curls up into a scroll. It this is then sucked into a glass pipette (similar to the ones many people will have used in school chemistry lessons) and is injected into the patient’s eye through an incision less than 3mm in size. The technique required to uncurl and position the transplanted tissue involves using extremely small bubbles of air and tiny squirts of fluid. At no point is the tissue touched with instruments as this would damage the extremely delicate endothelial cells. Finally, once in place, the tissue is pressed against the back of the patient’s cornea with an air bubble at high pressure for a few minutes until it has stuck. No stitches are required because the wound is so small.
The procedure is carried out under general anaesthesia and the patient is kept in hospital for one night following surgery. By the first outpatient appointment one week later the new endothelial cells are working and the cornea is clearing. Typically by one month the vision will be more or less good enough to drive and by two or three months the vision will be at or close to that of a normal eye. There are no restrictions on how active the patient is after the operation as the wound is so small and strong.
CASE STUDY - Mr Terry Walker
Mr Terry Walker, a 78-year-old retired waste management consultant from Pontesbury, had used the same prescription glasses for more than 60 years. In 2007 deterioration in vision caused him to consult with his optician who diagnosed FCD, an inherited genetic disorder. Further consultation with Mr Ewan Craig, a Consultant Ophthalmologist and Lead Clinician at The Shrewsbury and Telford Hospital NHS Trust, confirmed the diagnosis and also a cataract problem in both eyes.
During 2007/08 both eyes were successfully treated for cataracts resulting in an immediate and significant improvement in colour perception and clarity. Further surgery was felt unnecessary at the time.
By 2010 further deterioration in vision had occurred and on April 13 of that year a DMEK procedure was carried out under general anaesthetic. Mr Walker was discharged the following morning and given anti-rejection eye drops.
Two weeks later a post operative examination showed that:
vision had improved from 6/60 to 6/12 (very nearly good enough vision to drive)
cell density was 2,200sq mm – which is about four times that required to keep the cornea clear
the central cells were already active in giving improved clarity.
Mr Walker said: “I consider myself to be extremely fortunate to have been treated by such a dedicated and gifted surgeon and cannot wait to have my other eye treated. I also thank the unknown person who donated the cornea, so crucial to my treatment and would urge everyone to consider the gift of their organs for transplant before they die, as we all must.
“Finally I must thank the NHS in general and the Royal Shrewsbury Hospital in particular for providing such a superb service which will improve the quality of my remaining life.
“The increase of about 11 years in life expectancy since 1948 is, in my opinion, testimony to the vision of our government in the inauguration of the National Health Service.”
Mr Walker said the support group, available on www.fuchs-dystrophy.org.uk, has been extremely useful in exchanging coping strategies with other sufferers in the UK.