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Surgeons Offer New Treatment for Degenerative Eye Disease

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Duke Health News 919-660-1306

DURHAM, N.C. -- Researchers at Duke Eye Center believe a
surgical procedure they have refined for over a decade can
offer hope to more people suffering from end-stage age-related
macular degeneration (AMD). AMD is an eye disease that may lead
to central vision loss and afflicts an estimated 500,000 people
worldwide each year. The surgical procedure helps to restore
central vision, but is not a cure for AMD, the researchers
said.

The procedure, called "macular translocation surgery with
360 degree peripheral retinectomy" (MT360), is a two-stage
surgery that involves first internally rotating the retina to
shift the degenerating macula to a healthy area, away from
abnormally growing blood vessels and scar tissue. In the second
procedure, the eye is rotated to account for the ensuing tilt
in a person's visual field. The macula is the central portion
of the retina and is used for activities that require
fine-detail vision, such as reading or sewing.

"Until now MT360 had been used in patients with recent
central vision loss from AMD in their newly affected second
eye, but it hadn't been evaluated in patients who had undergone
previous macular treatment," said Cynthia
Toth, M.D.
, associate professor of ophthalmology and an eye
surgeon at Duke. "We now have shown that this may be an option
for patients who are experiencing continued vision loss despite
previous treatments for AMD. This technique often allows us to
recover a patient's reading vision. It isn't a cure, but our
patients' feedback has been very exciting."

The latest Duke research into MT360 appears in the Nov. 1,
2003, issue of the American
Journal of Ophthalmology. The authors are reporting that
patients who have received a round of a standard treatment
called ocular photodynamic therapy (PDT) and continue to
experience vision loss recovered reading vision after
MT360.

Macular degeneration, a disease that may cause blurring of
central vision, occurs in two forms, wet and dry. The dry type
is more common and occurs when deposits, called drusen,
accumulate under the retina. The dry type may set the stage for
the less common but more severe wet form in which blood vessels
and scar tissue begin to grow abnormally beneath the retina,
leading to permanent damage of the macula.

The macula is located at the center of the retina, the
light-sensitive tissue lining the back of the eye. The retina
converts light, or images, into nerve impulses that are carried
to the brain via the optic nerve. People with AMD may gradually
lose their central vision, which can seriously impact their
quality of life.

The procedure requires the efforts of two surgical teams.
One, led by Toth, has worked to perfect the MT360 technique,
which was pioneered by Duke eye surgeon Robert Machemer, M.D.,
who is now retired. The second team, led by Sharon Freedman,
M.D., associate professor of ophthalmology at Duke, has
developed the eye muscle surgery that works in tandem with
MT360. The procedure offers the possibility of restoring
reading vision to patients with end-stage, or wet, AMD.

"While not everyone is a candidate, we now have more
options," added Toth. "I once had to tell patients, if they had
bad scarring in their eyes and we had already tried
conventional therapies, that we were out of options. It's
rather rewarding to be able to help someone who can now see
pictures of their grandchildren or who can read again."

During the first phase of MT360, called "macular
translocation surgery," a surgeon detaches the retina and
rotates it, using the optic nerve as the pivot point, thus
moving the macula to a healthier area, away from the abnormally
growing blood vessels. Because of the rotation, however, a
tilted field of vision results.

The "tilt" is corrected during a second procedure in which
four of the six muscles that hold the eye in place are
adjusted. The muscles are detached from the outer wall of the
eye, called the sclera, allowing the eye to rotate into a
position that can counteract the relocation of the macula. The
muscles are then reattached. The second procedure is typically
done about two months after the first, allowing the eye to heal
from the initial phase of surgery.

According to the researchers, the retinal surgery would not
be possible without the partnership of eye muscle surgeons who
were able to develop a way to counteract the ensuing tilted
field of vision.

Not all patients with AMD are considered candidates for
MT360, the researchers said. The best candidates are those who
have central vision loss in one eye and have experienced recent
vision loss -- specifically within the previous six-months --
in their second eye. AMD affects each eye at different
rates.

The researchers are quick to point out that, as with any
surgical procedure, there are risks involved with MT360.

"Patients can experience retinal detachment or other
complications such as bleeding that are associated with any eye
surgery," Toth stressed. "Fortunately, we have lowered the risk
from about a 40 percent rate of retinal detachment to less than
10 percent. Double-vision or residual tilting may also occur,
which we can treat with the use of special glasses or
occasionally with additional muscle surgery."

Age appears to be the main risk factor for developing AMD.
According to the researchers, a person's chance of developing
the disease increases with each passing decade after age 50,
with 30 percent of people over age 70 exhibiting some sign of
the disease. The biggest environmental and genetic risk factors
include smoking and a family history of the disease.

"Macular degeneration is becoming epidemic as the life
expectancy of our society continues to increase," said Michael
Cooney, M.D., assistant professor of ophthalmology and director
of the AMD center at Duke. "The macular translocation procedure
is continuing to improve as we learn more and our
instrumentation advances."

The dry form of AMD is much more common than wet, occurring
in more than 85 percent of all people with intermediate and
advanced forms of the disease. Two-thirds of patients with
advanced AMD have the wet form, which is the most severe and
leads to significantly more vision loss, according to the
researchers. Approximately one in 10 patients with dry AMD will
eventually convert to the wet form, which accounts for 90
percent of vision loss in patients with AMD. A patient's
average chance of moving from the dry to wet form is about 2
percent per year.

While there are no treatments that can prevent vision loss
in AMD patients, there are treatments that can slow its
progression.

"Treatments are limited, but we're making steady progress in
developing new options at Duke," Cooney said, "Our goal is to
focus on delivering high-quality care to our patients based
upon the latest research and to anticipate and meet as many
needs of our AMD patients as possible. It isn't enough to say
'we're sorry, but there is nothing more we can do for
you.'"

Research funding for the PDT study was provided by Euan and
Angelica Baird, benefactors of Duke Eye Center. Some of the
research facilities used during the study are supported by a
grant from the National Institute of Health. Carl Park, M.D., a
vitreoretinal surgeon and former associate at Duke Eye Center,
is an author on the article. Park now practices in
Philadelphia.

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