(DSEK, PK & DALK)
The cornea is the transparent dome of tissue that forms the front coat of the eye. It is responsible for the majority of the focusing power of the eye. Any condition that reduces the transparency of the cornea will result in loss of vision.
The cornea is comprised of several layers. The outer layers of the cornea are typically affected by conditions such as Keratoconus or by trauma or infection. The innermost layer of the cornea is called the Endothelium. This is specifically affected by a genetic condition called Fuchs’ Dystrophy where acceleration of the natural process of loss of endothelial cells results in swelling of the cornea.
Animation explaining how a Cornea Transplant works
Traditionally, most corneal transplant surgery has involved replacing a full thickness disc of the cornea for disc of cornea from a donor. This procedure is called Penetrating Keratoplasty or PK. Today, it is considered preferable to replace only those layers (or lamellae) affected by the specific condition affecting that layer and to leave those layers unaffected in place, thus reducing the amount of tissue transplanted. This approach is called lamellar corneal surgery and leads to quicker recovery of vision, it is also thought that in the long term this will result in fewer transplants being rejected by the recipient and this data is increasingly supported by research and audit in this field.
David Anderson has been performing lamellar corneal surgery for over 10 years and has active research interests in corneal transplant surgery including DSEK in which he has contributed to the development of current surgical techniques (see Research). David’s further training in corneal transplant surgery took place in 2000 when he spent 18 months at Moorfields Eye Hospital as a Fellow in Corneal Surgery following a period of one year studying advanced corneal and ocular transplant surgery techniques as a TFC Frost Scholar at Bascom Palmer Eye Institute in Miami, USA.
Descemet Stripping Endothelial Keratoplasty (DSEK)
(Please read in conjunction with NICE Guidance IPG304)
DSEK is a procedure designed to replace corneal endothelial cells lost through either genetic decline in Fuchs’ Dystrophy or following certain forms of surgery i.e. Pseudophakic Bullous Keratopathy.
Animation explaining the DSEK procedure
In DSEK a thin layer of cornea including the endothelial cell layer is injected into the eye through a small entry port 4-5mm in size using a device called an EndoSaver. The disc of tissue which typically measures a tenth of a millimeter (100 micrometers) in thickness comprises the endothelial cell layer, Descemet’s Membrane and a small amount of corneal substance or stroma. This thin lenticule, normally between 8-9mm in diameter is unfolded in the eye, then further stretched using air to attach it to the underside of the cornea. One stitch is typically required which is usually removed two weeks later, this is painless.
DSEK offers the advantages of more rapid visual rehabilitation than PK. It typically results in a far smaller change in spectacle prescription and has now become the new ‘Gold Standard’ for corneal transplantation for endothelial failure. David Anderson has been performing DSEK since 2007 and is considered to be an expert in this technique. He has published and presented work on DSEK internationally and teaches this surgery to Ophthalmologists from around the world (see Research).
What does the surgery involve?
Surgery typically takes place under general anaesthesia although local anaesthesia may also be used. Patients usually return home on the day of surgery but can stay overnight as it is desirable to lie flat looking up at the ceiling for the first day or two to maximize contact between the air bubble and the transplant.
Frequent eyedrops are required initially which are then reduced over time. Patients can return to normal activities a week or two following surgery.
Penetrating Keratoplasty (PK)
PK was first performed in 1905 and so is a very well characterized operation. David Anderson routinely performs PK and teaches this surgery on the Corneal Fellowship program at University Hospital Southampton.
What does surgery involve?
PK is usually performed under general anaesthesia with the first review on the first post-operative day. It is useful to think of a corneal transplant as a process rather than a one-off surgical event e.g. cataract surgery.
All transplant operations rely on the bodies’ natural tendency to reject foreign tissue being medically suppressed with drugs. For a routine corneal transplant this usually involves using eye drops (with decreasing frequency) for approximately 18 months.
The final best-corrected vision may only be achieved through the use of spectacles or contact lenses although further surgery to enhance visual outcomes following PK include laser vision surgery and the use of astigmatism correcting intra-ocular lenses.
What results may I expect?
The outcomes of corneal transplantation have been most extensively studied using data from the Australian Corneal Graft Registry. Broadly, these outcomes can be divided into two major groups: Visual outcomes and survival outcomes. Both groups depend very much on the condition of the eye prior to the graft being performed. Conditions which result in inflammation, infection or blood vessels entering the eye are associated with worse outcomes than those which do not. Pregnancy, prior blood transfusion and a failed previous graft are also recognised as risk factors (albeit lesser) for graft survival. Overall approximately 60% of grafts are functional at 10 years(rising to >90% in the best cases). Visual outcomes also vary according to the reason for which the graft was performed.
Are there any risks with the surgery?
All operations carry the risk of complications whether from the anaesthetic, surgical procedure, subsequent medical procedures e.g. removal of stitches or any drugs e.g. eye drops which need to be taken. The risk of retinal detachment following a corneal transplant is estimated at about 2% (twice that for cataract surgery), and sight threatening infection about 1% (five times higher than for cataract surgery). The donor material is screened for HIV, Hepatitis and the presence of bacterial infection and is assessed for quality at the Eye Bank in Bristol administered by the UK Transplant Centre. There always, however, remains a risk that a serious transmissible disease may be passed from the donor to the recipient although that risk is thought to be extremely small (<1%).
Deep Anterior Lamellar Keratoplasty (DALK)
DALK is a technique in which all of the corneal tissue in front of Descemet’s Membrane is replaced leaving the recipients natural endothelial cell layer intact. DALK is particularly useful when conditions which affect only the front of the cornea such as Keratoconus or conditions which cause scarring are present as by leaving the recipients natural endothelial cells in place, the risk of corneal transplant rejection are lowered.
DALK was pioneered as a technique by Dr Gerrit Melles, a Dutch Ophthalmologist. David visited Dr Melles in Rotterdam to train in DALK and has been performing this surgery from 2000 to the present time.
For DSEK, PK and DALK post-operative surgery information can be downloaded here answering commonly asked questions.
To arrange treatment please contact:
Anita Summerfield DD: 023 80258 421
firstname.lastname@example.org for further information.