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Source: http://www.scienceblog.com/cms/node/7710
Artifical cornea lets woman blind 20 years see
A severe allergic reaction to a medication robbed Elma Phifer of her
vision two decades ago when she was 39. The reaction scarred her corneas
and reduced the ability of her eyes to soothe their damaged surfaces by
remaining moist.
She came to rely upon family and friends to help her do many of the
activities people with normal vision sometimes take for granted. Now,
twenty years and several life milestones later, Elma is able to see again,
thanks to advances in ophthalmology research.
Physicians at Duke University Eye Center and Harvard have been monitoring
her closely following the implantation of an artificial cornea, or
keratoprosthesis, into one of her eyes -- restoring her sight in that eye
and ultimately helping her regain much of her independence. Phifer is one
of several hundred patients nationwide who have received such artificial
corneas, which have revolutionized the treatment and care of patients like
her.
"I was blind for twenty years in both my eyes," Phifer says. "A regular
cornea wouldn't work because of the severity of damage to my corneas. But
now my life is more like normal and I can do more things on my own and
finally read the things that I want to read."
While many people with cornea damage are eligible to become candidates for
standard human cornea transplants, some cannot tolerate donor tissue. The
problem is not necessarily tissue rejection –- although in some cases it
is -- but rather progressive growth of blood vessels and scar tissue
throughout an implanted natural cornea, according to researchers. The new
cornea eventually becomes as opaque as the original.
"The cornea is usually just like a clear window in the eye for people to
see through, but sometimes the cornea becomes opacified and people can no
longer see," said Natalie Afshari, M.D., an ophthalmologist specializing
in cornea and refractive care at Duke University Eye Center and one of the
few surgeons performing the implantation of artificial corneas in the U.S.
"We're able to care for some patients by putting in a prosthetic cornea so
that they can see out again, and their doctors can see in."
The development of opacity in the cornea is typically the result of
inflammation due to disease. Sometimes it is the result of injuries, like
damaging chemicals accidentally introduced into the eye, Afshari added.
The artificial cornea is entirely manmade, but does utilize donated
corneal tissue, said Afshari. Available devices include a front and back
plate, which would first be attached to a donated cornea and then sewn
into the recipient's eye. First, the surgeon cuts a hole from the center
of the donated cornea so that the "keratoprosthesis" can be inserted into
it.
The next step depends on the artificial cornea model being used, but
typically includes connecting a front plate to a back plate with the donor
cornea tissue sandwiched in between. The surgeon then removes most of the
damaged cornea from the patient's eye so that the new prosthesis can be
sewn into place using sutures to connect the donor tissue and
keratoprosthesis to the patient's remaining corneal tissue.
"Getting an artificial cornea is not an easy ride for the patient,"
Afshari warns. "We carefully screen each candidate and educate them about
the lifetime commitment involved with the keratoprosthesis. Patients
require a lot of follow up to make certain the artificial cornea remains
structurally sound and healthy."
Because the artificial cornea is a foreign body, it doesn't "heal" the way
a wound would and become a part of the body. There could be complications
over time, such as thinning of the tissue surrounding the implant or the
development of glaucoma due to preexisting imperfections in the draining
mechanics of the eye, according to Afshari.
Infections are always a risk, which is why every patient must adhere to a
strict daily regimen of antibiotic eye drops. With regular maintenance –
including visits to the ophthalmologist at least every three months (more
frequently immediately after surgery) – complications can be kept to a
minimum, she said. Because of the intensiveness of the lifetime commitment
to follow up, the procedure is rarely performed in children.
Many researchers credit Claes Dohlman, M.D., chairman emeritus of
ophthalmology at Massachusetts Eye and Ear Infirmary and Harvard Medical
School as a "father" of modern cornea science. Dohlman has developed the
concept of one such keratoprosthesis for more than forty years.
Despite his advancing age of 82, Dohlman has managed to refine a type of
artificial cornea widely known as the Boston keratoprosthesis. He has made
more than 300 of the devices himself, but holds no financial interest in
the success of the artificial cornea.
"We've been fortunate to see gradual improvement in the use of the
keratoprosthesis over the years," Dohlman said. "A series of steps have
resulted in good long-term retention and stability, as well as good
vision, in patients. We will continue to do research and development in
this area so that we can make the devices even safer and less expensive in
the future."
Both Afshari and Dohlman agree that their hope is for increased use of
keratoprosthesis in the third world.
"Worldwide, corneal blindness is a major problem due to infections, fewer
physicians and problems with hygiene," says Afshari.
The major hurdle right now, according to Dohlman, is the cost of the
procedure. "The healthcare system in poor countries cannot afford such
devices right now, but in a few decades that situation may be different,"
he said.
It isn't the cost of the device itself that is the problem, according to
Dohlman. Rather, it is the prohibitive cost of the frequent post-operative
visits, the travel required, the medications and contact lenses used in
follow up with the patients.
For now, however, the devices are becoming more available as more doctors
are trained in the procedure and care of the post-operative patient. And
for people like Elma Phifer, that has made all the difference.
From Duke University Medical Center
By BJS at 04/28/2005 - 12:12 | bioscience & medicine | login or register
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Copyright 2005, Science Blog.
Staring directly at the Sun, so you don't have to.
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"Ethics" is simply a last-gasp attempt by deist conservatives and
orthodox dogmatics to keep humanity in ignorance and obscurantism,
through the well tried fermentation of fear, the fear of science and
new technologies.
There is nothing glorious about what our ancestors call history,
it is simply a succession of mistakes, intolerances and violations.
On the contrary, let us embrace Science and the new technologies
unfettered, for it is these which will liberate mankind from the
myth of god, and free us from our age old fears, from disease,
death and the sweat of labour.
Rael
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