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Update
Cornea
Günther Grabner – g.grabner@salk.at
SURFACE REPAIRS
Expanding range of options is making
ocular surface disease more treatable
by Roibeard O’hEineachain in Prague
A
clear treatment protocol is emerging for treating
severe ocular surface disease, with therapies
ranging from amniotic membrane transplantation
to the implantation of keratoprostheses, said
Günther Grabner MD in a keynote lecture in a Cornea Day
session at the 16th ESCRS Winter Congress.
“In most cases you can do autologous stem cell
transplantation plus amniotic membrane plus, if required,
penetrating keratoplasty. When there is a bilateral loss of
stem cells but a wet surface, a Boston keratoprosthesis is
the treatment of choice, but if the eye is dry I think nothing
beats the modified osteo-odonto keratoprosthesis,” said Dr
Grabner, Paracelsus Medical University, Salzburg, Austria.
Dr Grabner noted that amniotic membrane has a wide
variety of uses in ocular surface reconstruction. It can
be used as an “inlay”, as a sort of replacement basement
membrane, as an “onlay” where it can serve as a bandage
contact lens, and it can be placed in multiple layers as an
alternative to superficial lamellar keratoplasty. There have
also been reports of its use in the treatment of bullous
keratopathy and neurotrophic ulcers as well as in pterygium
surgery and revision of filtering blebs.
Nowadays it is also widely used as a substrate for cultured
limbal cells for use in limbal autograft procedures. The
usual indications for such techniques are limbal stem cell
deficiency resulting from burns, chemical injury, trauma
or disease. The loss of limbal stem cells leads to permanent
epithelial defects stromal scarring and symblepharon, Dr
Grabner noted.
“In cases with unilateral complete stem cell loss, amniotic
transplantation is not sufficient because it will not replace
the stem cells. What we need to do is in autologous
limbal stem cell transplantation plus/minus penetrating
keratoplasty,” he added.
The most frequently performed limbal stem cell
transplant procedure is a conjunctival limbal autograft
from the fellow eye. The advantage of autografts is that
they entail no risk of immune rejection and, unlike limbal
allografts, do not require the use of intensive long-lasting
systemic immunosuppression. The main, however minimal,
disadvantage is that they require surgery on the normal eye.
“
In cases with unilateral complete stem
cell loss, amniotic transplantation
is not sufficient because it will not
replace the stem cells. What we need
to do is in autologous limbal stem
cell transplantation plus/minus
penetrating keratoplasty
Günther Grabner MD
EUROTIMES | Volume 17 | Issue 10
Ex-vivo expansion of limbal stem cells on an amniotic
membrane substrate can maximise the amount of limbal
stem cells available for transplantation, he noted. He and
his associates have initiated a study that will examine the
feasibility of using buccal stem cells as an alternative in
such cases.
Role of keratoprostheses In patients with bilateral
limbal stem cell insufficiency, limbal allografts from a family
member or a cadaver eye are one alternative. However, such
transplants again involve intensive immunosuppression and
have a fairly low rate of success. As a result, corneal surgeons
are increasingly turning to the use of keratoprostheses in
such cases, he said.
There are several designs of keratoprosthesis available
but there are only two that are widely used today. They are
the Boston KPro type 1, developed at the Massachusetts
Eye and Ear Hospital developed by Claes Dohlman, and
the osteo-odonto-keratoprosthesis (OOKP) first developed
by Strampelli in the 1960s and later improved upon by
Falcinelli.
The decision of which type of keratoprostheses to use
depends on the condition of the eye and the condition of the
patient, Dr Grabner said. The standard Boston KPro has a
nut and bolt design and consists of two 0.9mm-thick PMMA
plates clamped onto a donor button of corneal tissue which
is sutured into the recipient's eye, he said. Its indications can
include eyes with limbal stem cell insufficiency, but its use
requires a wet eye with good blinking function.
The OOKP uses an osteodental lamina overlaid with
buccal mucous membrane as a skirt for its PMMA optic. It
can also be used in eyes with limbal stem cell insufficiency
and severe keratoconjunctivitis sicca, Dr Grabner said.
However, owing to the difficult and time-consuming
nature of its implantation, the OOKP is usually reserved
for patients with bilateral corneal blindness resulting
from severe end stage corneal disease, for eyes injured by
chemicals or burns, and for severely dry eyes.
Implantation of the Boston K-Pro type 1 is only slightly
different from a standard penetrating keratoplasty, he
noted. As a result, it has become the most widely used
keratoprosthesis in the world, with around 1,000 implanted
every year and close to 100 surgeons implanting them. One
drawback with the Boston K-Pro type 1 is that it requires the
patient to commit to lifelong use of topical antibiotics and
bandage contact lenses, he said.
Most other types of keratoprostheses have fallen into
disuse, Dr Grabner noted. For example, the AlphaCor
keratoprosthesis, which has indications similar to
those of the Boston K-Pro is no longer promoted by its
manufacturer, possibly because of the poor retention rate
some authors have reported with the implant. However,
the Temprano keratoprosthesis – which uses a piece of
autologous tibia bone as a skirt – remains a useful option in
patients with dry eyes who have no teeth that could be used
for an OOKP.
Courtesy of Günther Grabner MD
18
Case 1, lye burn, 2 failed PKP, VA hand motion
Case 1, 18 months’ post-op, VA 0.8
Patient with OOKP after healing
Dr Grabner cautioned that implants like the OOKP put
the patient at an additional risk for glaucoma. However, the
risk of onset or progression of glaucoma induced in this way
will be much lower when IOP is controlled from early on
with a glaucoma drainage implant, he noted.
“If you have a bilateral dry eye case I think nothing beats
the OOKP and this is what you should advise your patient
to have. You certainly need specialised centres and if you
put a cosmetic shield on top of it, it is very difficult to tell
which one of the eyes is the one with the keratoprosthesis,”
he added.