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This is a type of corneal transplant
Lap Joint Keratoplasty
Robert C. Arffa, M.D.
People who cannot see well because their cornea is cloudy could benefit from a corneal
transplant. This is a study of a variation on the standard corneal transplant surgical
technique. The new technique is being studied because it has potential advantages over the
currently accepted technique. Prior to this study the procedure was performed on a small
number of patients, and promising results were obtained. However, since it is a new
technique potential results, including the benefits of this technique over the standard
technique, and the risk of complications, are not fully known.
What is a corneal transplant?
The cornea is a clear membrane in front of the colored part of the eye, the iris, and the pupil.
It is like the glass front of a camera lens. The light passes through the cornea before being
focused by the lens to form an image on the back of the eye, the retina. If the cornea is not
clear, or its shape is distorted, the light does not pass through it normally, and a proper
image does not reach the back of the eye.
One of the most common reasons for the cornea to become cloudy is swelling due to
“endothelial cell” failure. The endothelial cells line the back (inner) surface of the cornea.
They maintain the normal fluid balance of the cornea by constantly pumping water out of
the cornea.
Each cornea is endowed with a fixed number of endothelial cells at birth, and these cells do
not reproduce. They gradually decrease in number over our lives. Certain ocular conditions
can damage or destroy corneal endothelial cells, including trauma, cataract surgery,
glaucoma, and infection. If the density of endothelial cells falls below a minimum value, the
cornea becomes swollen and cloudy. This can markedly decrease vision and often causes
light sensitivity and pain.
In such cases the only means of restoring a clear cornea and vision is through transplantation
of endothelial cells from a human donor. The traditional technique is called penetrating
keratoplasty. The central portion of the patient’s diseased cornea is surgically removed and
replaced with a similar portion from a human donor cornea. The common name of this
procedure is corneal transplantation.
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On average, the chance of obtaining a clear cornea after a penetrating transplant is
approximately 85%. However, there are some significant problems with our current
technique. It takes approximately one year for the wound to heal sufficiently to permit
removal of all supporting stitches. In most cases good vision must await prescription of new
glasses. Typically new glasses can not be prescribed for at least 6 months, and in some
cases not until after all stitches are removed one year after surgery.
As mentioned above, good vision is dependent on the corneal surface having a regular
curvature. This is difficult to obtain with corneal transplant surgery. On average transplanted
corneas have moderate distortion of their surface. Distortion or deviation from a spherical
curvature is called astigmatism.
In most cases this astigmatism can be corrected with glasses. In some cases good vision can
only be obtained with a rigid contact lens, or through surgical reduction of astigmatism.
The Lap Joint Keratoplasty Technique
Drs. Robert Arffa, Pittsburgh, PA and Massimo Busin, Forli Italy, have devised a variation
of the standard corneal transplant technique, which is designed to reduce problems currently
observed.
Simply put, the new technique involves :
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creating a donor cornea with an inner (posterior) lip around the
circumference
2.
creating a matching inner groove on the patient’s cornea
3.
sewing the new corneal tissue in place
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The researchers hope that this technique will result in much more rapid healing than with the
current technique. This should permit fitting with new glasses or a contact lens
approximately 4 months after surgery (instead of 6 to 15 months with the current technique).
Also, they hope that astigmatism or distortion of the corneal surface will be less than with
the current technique.
The purpose of this study is to determine whether or not this new technique permits faster
healing and reduces astigmatism. Prior to beginning this study, 12 patients underwent Lap
Joint Keratoplasty surgery. With short-term follow-up of these patients, the results have
been very good. Therefore this study will involve additional patients, with closer
monitoring of the results.
Risks of Lap Joint Keratoplasty
Risks of Standard Corneal Transplant Surgery
Corneal transplant surgery, as with any surgical procedure entails risk, both to your eye and
to the rest of your body. The risks are similar to those of cataract surgery, or any other
surgical procedure in which the eye is opened. The risks of endokeratoplasty are almost
identical with those of standard corneal transplant surgery. Some of the more common or
more serious possible complications follow:
There is a small risk from administration of anesthesia. Sedative agents will be administered
intravenously, and there is a risk of abnormal reaction. The eye will then be numbed by
injection of a local anesthetic. There is a very small risk (<1 in 1000) of sight-threatening
complications of this injection.
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Any time that surgery is performed inside the eye, there is a risk of bleeding or infection
developing in the eye. Precautions are taken to prevent this from occurring. Even if such
problems develop, in most cases good sight can be maintained with treatment.
Increased pressure inside the eye (glaucoma) can occur after surgery. If you have glaucoma
before the surgery, the condition can worsen. The pressure usually can be controlled with
eye drops or medicine by mouth, but further surgery may be required in extreme cases.
The retina is where the image forms in the back of the eye. The retina converts the light to
electrical energy, which is transmitted by the optic nerve to the brain. Damage to the retina
(swelling or detachment) can occur after any surgery in which the eye is opened.
It is often necessary for your skin cells (epithelium) to heal over the new cornea. Usually
this occurs within one week of surgery. However, some patients are slow to heal, and
patching, use of a bandage soft contact lens, or stitching the lids closed may be necessary.
Until the surface cells heal there is an increased risk of infection or ulceration of the cornea
Since the new cornea is from another person’s eye, your body may recognize it as foreign.
If that occurs, your body may “reject” the new tissue. Approximately half of the time this
reaction can be stopped, particularly if treatment is started promptly. However, rejection is
the most likely complication of corneal transplantation.
If the new cornea is rejected, it will become cloudy and your vision will probably be limited
to finger counting. Repeat corneal transplantation can be performed, however, the risk of
rejection is increased.
Eye donors are screened to eliminate those with diseases that could be transferred to you via
the donor cornea. The donor’s general and eye medical history are reviewed, and blood tests
are performed for hepatitis and AIDS (HIV infection). AIDS has never been transmitted via
a corneal transplant, but we test for it as a precaution. While none of these tests are
infallible, there is only a remote chance of transmitting disease via corneal transplantation.
It is not possible to list all possible complications of corneal transplant surgery. Other
complications can occur that may reduce your sight, or cause you to lose your sight or your
eye. Overall there is a less than 1 in 100 chance of losing your sight or your eye.
Additional Risks of Lap Joint Keratoplasty
The Lap Joint Keratoplasty technique involves making a peripheral “lap joint” between the
donor cornea and your cornea. If the two halves are not proper thickness the donor corneal
surface could end up slightly above or below the natural surface. This may delay healing.
It is possible that irregular healing of the corneal flap after the Lap Joint Keratoplasty
procedure could result in a distorted cornea. This would mean that glasses would not correct
the vision, and rigid contact lens wear may be necessary. The researchers think that the risk
of this is less than the risk with standard transplant surgery, but this is not certain.
There is a small risk that the corneal skin cells (epithelium) may grow into the lap joint
portion of the wound. Treatment of this condition involves lifting the edge and clearing the
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cells. Untreated growth of epithelium within the wound may distort vision and may actually
damage the wound if severe and progressive. Small ingrowths do not usually present any
visual problems and need only to be monitored.
The donor cornea must be prepared with a slightly more complicated technique than in
standard corneal transplant surgery. If this procedure is not successful, the cornea may not
be suitable for transplantation. Dr. Arffa or Dr. Busin will make every effort to make sure
that a second cornea is available. However, in some cases surgery may have to be cancelled
and rescheduled.
If the endokeratoplasty technique is not successful in restoring healthy endothelial cells and
a clear cornea, standard corneal transplant surgery can be performed. It is expected that the
chance of success of this surgery will not be impaired by the lap joint keratoplasty
procedure.
Only a small number of patients have undergone lap joint keratoplasty, and observation of
those patients has only been for a short period. Therefore the exact risks, both short and
long-term, and their likelihood are not fully known.
If other complications are encountered during this study, you will be informed of them.
Cornea after Lap-joint keratoplasty with suture still in (left) and after suture was removed
(right)
Benefits Of Lap Joint Keratoplasty
Based on our experience with this procedure and with other related procedures, we think that
there are potential benefits of lap joint keratoplasty over current corneal transplant
techniques. The researchers hope that this technique will result in more rapid healing, that
should permit fitting with new glasses or a contact lens approximately 4 months after
surgery (instead of 6 to 15 months with the current technique). Also, we hope that
astigmatism or distortion of the corneal surface will be less than with the current technique.
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By serving as one of the early patients to undergo lap joint keratoplasty, you will benefit
others. If this technique proves to be superior, it will be used to improve the sight of
thousands of other people with endothelial failure.
Alternative Procedures
The only way to improve your vision is through corneal transplantation. Standard corneal
transplantation through penetrating keratoplasty is successful in a high percentage of cases.
Approximately 85% of patients undergoing penetrating keratoplasty will obtain a clear
cornea. However, it takes approximately one year for the wound to heal sufficiently to
permit removal of all supporting stitches. In most cases good vision must await prescription
of new glasses, and this can not be done for at least 6 months, and in some cases not until
after all stitches are removed one year after surgery.
Distortion or deviation from a spherical curvature, or astigmatism, is very likely after
penetrating keratoplasty. In most cases this astigmatism can be corrected with glasses. In
some cases good vision can only be obtained with a rigid contact lens, or through surgical
reduction of astigmatism.
Follow-up Visits and Examinations
All patients will be seen in Dr. Arffa’s office at the following times after surgery: 1 week, 1
month, 2 months, 3 months, 6 months, and 1 year. These visits are necessary after
traditional corneal transplant surgery as well. During these visits eye examinations may
include determination of your vision with and without glasses or contact lens, obtaining a
computer-analyzed photograph of the surface of your new cornea, measurement of
intraocular pressure, measurement of cornea thickness using ultrasound, and photographing
the cells on the back of the cornea (specular microscopy). None of these tests are painful or
pose a risk of injury to your eye. They are standard examination techniques typically
performed after corneal transplantation.
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