African
Americans at High Risk of Glaucoma
African-Americans
have six times the incidence of glaucoma compared to whites, according
to Emory glaucoma specialist Mary Lynch, and researchers are still trying
to find out why.
Not only are blacks at extremely high risk for the potentially blinding
pressure within the eye that characterizes glaucoma, but they also experience
more aggressive forms of the disease, said Lynch, associate professor
of ophthalmology at the School of Medicine, chief of ophthalmology at
the Veterans Affairs Medical Center and a council member of the Georgia
Society of Ophthalmology.
She and other members of the society's governing council met with the
Black Congressional Caucus of the Georgia legislature on Jan. 26 to
emphasize the importance of education and early detection of glaucoma
in African-Americans.
"We need to heighten awareness among members of the African-American
community about this potentially blinding yet preventable disease,"
Lynch said. "People may have glaucoma and not know it because symptoms
only become apparent once the disease has progressed. Getting a simple
glaucoma test is simple -- and can be sight-saving."
Researchers do know that the racial disparity in glaucoma incidence
cannot be attributed to lack of access to medical care or insurance,
as is sometimes the reason for disparities in incidence of other diseases.
They also know that if caught early enough, much of the vision damage
associated with the condition can be stalled or halted.
Lynch and her colleagues are gathering important information on glaucoma
in African-Americans through Emory's participation in two of the largest
federal glaucoma studies in the nation. The Emory group has recruited
more patients for the multi-center Advanced Glaucoma Intervention Study
than any other participating medical center. The group also is studying
patients with increased pressure within the eye who have not yet developed
glaucoma symptoms as part of the Ocular Hypertension (high blood pressure)
Treatment Study (OHTS). Both studies are funded by the National Eye
Institute of the National Institutes of Health.
Those interested in participating in the OHTS program may call 248-4134.
What is Glaucoma?
Glaucoma is a group of eye diseases that gradually steals sight
without warning and often without symptoms. Vision loss is caused
by damage to the optic nerve. This nerve acts like an electric
cable with over a million wires and is responsible for carrying
the images we see to the brain.
It was once thought that high intraocular pressure (IOP) was
the main cause of this optic nerve damage. Although IOP is clearly
a risk factor, we now know that other factors must also be involved
because even people with "normal" IOP can experience
vision loss from glaucoma.
Different Types of Glaucoma
The two main types of glaucoma are open angle glaucoma, or primary
open angle glaucoma (POAG), and angle closure
glaucoma.
Primary Open Angle Glaucoma
This is the most common form of glaucoma, affecting about three
million Americans. It happens when the eye’s drainage
canals become clogged over time. The inner eye pressure (also
called intraocular pressure or IOP) rises because the correct
amount of fluid can’t drain out of the eye. With open
angle glaucoma, the entrances to the drainage canals are clear
and should be working correctly. The clogging problem occurs
inside the drainage canals, like the clogging that can occur
inside the pipe below the drain in a sink.
Most people have no symptoms and no early warning signs. If
open angle glaucoma is not diagnosed and treated, it can cause
a gradual loss of vision. This type of glaucoma develops slowly
and sometimes without noticeable sight loss for many years.
It usually responds well to medication, especially if caught
early and treated.
Angle Closure Glaucoma
This type of glaucoma is also known as acute glaucoma or narrow
angle glaucoma. It is much more rare and is very different from
open angle glaucoma in that the eye pressure usually goes up
very fast. This happens when the drainage canals get blocked
or covered over, like the clog in a sink when something is covering
the drain. With angle closure glaucoma, the iris and cornea
is not as wide and open as it should be. The outer edge of the
iris bunches up over the drainage canals, when the pupil enlarges
too much or too quickly. This can happen when entering a dark
room.
A simple test can be used to see if your angle is normal and
wide or abnormal and narrow. Treatment of angle closure glaucoma
usually involves surgery to remove a small portion of the outer
edge of the iris. This helps unblock the drainage canals so
that the extra fluid can drain. Usually surgery is successful
and long lasting. However, you should still receive regular
check-ups. Symptoms of angle closure glaucoma may include headaches,
eye pain, nausea, rainbows around lights at night, and very
blurred vision.
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