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DURHAM, NC — 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 with 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 the 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, MD, an ophthalmologist
specializing in cornea and refractive care at the Duke University Eye
Center and one of the few surgeons performing the implantation of
artificial corneas in the US. "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 pre-existing 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, MD, 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 being 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 says. "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.
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