Download DMEK latest in selective tissue corneal transplantation surgery

DMEK latest in selective tissue corneal transplantation surgery
Traditional corneal transplantation, known as Penetrating Keratoplasty (PK), is a highly
refined procedure which has been performed successfully since 1905 with positive overall
outcomes. Over the last decade, PK has evolved allowing surgeons to provide newer
techniques, such as Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) or
Descemet’s Membrane Endothelial Keratoplasty (DMEK), to patients with specific corneal
needs. These advanced surgical procedures involve replacing only the diseased portion of
the cornea with similar healthy donor corneal tissue, resulting in fewer complications and
more efficient use of precious donor material. This is in contrast to PK, in which the full
thickness of the cornea is replaced regardless of the corneal layer that is involved in the
disease process. At the Princess Alexandra Hospital (PAH) these newer surgical techniques
of corneal transplantation are rapidly becoming the preferred surgical choice for dealing
with corneal endothelial decompensation.
Figure 1:
Eye anatomy: The cornea is the clear dome over the coloured part of the eye (iris)
Figure 2.
Corneal anatomy: The cornea has several distinct layers
Figure 3.
Different corneal layers are replaced in different graft techniques
The corneal tissue used in these transplants is provided by Eye Banks. There are six Eye
Banks throughout Australasia. The QLD Eye Bank, located at Princess Alexandra Hospital, is
an amazing non-profit organization that obtains, medically evaluates and distributes
donated eyes to individuals for use in corneal transplantation. It provided over 580 donor
corneas this last year to QLD and other states.
DSAEK involves grafting a small portion of posterior stroma and Descemet’s membrane from
a healthy donor to the host cornea, whereas DMEK is a procedure in which only the
Descemet’s membrane and endothelium of the patient’s cornea are replaced. To put it
simply, DMEK is literally transplanting a single layer of cells, whereas DSAEK is transplanting
those cells along with a substantial layer of fibrous tissue. Consequently, DSAEK postoperative corneal thickness far exceeds the range of normal corneal thickness and the
donor-recipient interface is a stroma-to-stroma. DMEK post-operative corneal thickness
should be within the range of normal corneal thickness and donor-recipient interface is
Descemet’s membrane to stroma, ensuring a more natural, final anatomic result.
Furthermore, DMEK has faster visual recovery than traditional PK grafting and less refractive
error in the long-term. Regardless of all its positives, DMEK has slightly more challenges in
terms of the surgical techniques involved.
To describe a DMEK procedure, think of trying to un-roll a portion of Glad-Wrap in a bowl of
water, then imagine the bowl is the size of an eye! Firstly, a 2.6-mm clear corneal tunnel
incision is made. The anterior chamber is filled with air, and the Descemet’s membrane is
stripped off from the posterior stroma. From an organ-cultured donor corneo-scleral rim, a
9.0-mm-diameter "Descemet’s membrane roll" is harvested. Each donor “roll” is inserted
into a recipient anterior chamber, positioned onto the posterior stroma, and kept in
position by completely filling the anterior chamber with air.
As well as a quick visual recovery another advantage of DMEK over DSAEK is a 15 fold
reduction in rejection rate compared with older techniques! Fewer medications are
therefore required in both the short and long term (Anshu et al Ophthalmology
2012;119:536–540).
At PAH, Dr Andrew Apel, Senior VMO of Ophthalmology, specialises in Corneal Surgery and
External Eye Disease. He has been performing DSAEK procedures for the last four years, and
DMEK procedures for the last eighteen months, with great success on patients suffering
from corneal endothelial disorders such as Fuchs’ Dystrophy. This dystrophy would
ultimately result in corneal oedema, bullous keratopathy and painful loss of vision if left
untreated. Through the PAH mentor program, Dr Apel is ensuring young ophthalmologists
have a supportive environment to further develop their surgical skills and expertise.
Furthermore, opportunities exist for health and medical research in this delicate field of
corneal grafting.
In summary, DSAEK and DMEK are exciting new graft options available at PAH to provide
quick visual rehabilitation in the treatment of corneal endothelial disorders. DMEK in
particular is at the cutting edge of corneal transplantation and the results being achieved
are in some cases miraculous.
DSAEK
Figure 4.
DSAEK one year post-op
Epithelial bullous
DMEK
Figure 5.
DMEK one day post-op with epithelial bullous as Descemet’s membrane has still
not adhered 100%.
DMEK still to adhere
Figure 6.
Same DMEK as Figure 2 but 1 month post-op. Descemet’s membrane is almost
100% adhered-there is still an area slightly temporal to the pupil edge which needs
to adhere.
Figure 7.
Air bubble in anterior chamber pushing Descemet’s membrane roll flat onto host
cornea.
Figure 8.
Fold in DMEK at pupil edge viewed with slit-lamp.
Figure 9.
Good DMEK twelve months on.