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Glaucoma
Glaucoma is actually a group
of eye diseases that lead to damage of the optic nerve (the
nerve fiber that carries information from the eye
to the brain), which can then lead to vision loss and the
possibility of blindness. |
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Optic nerve damage usually occurs in the presence of high
intraocular pressure, but glaucoma can occur with normal or even
below-normal eye pressure.
There are two main forms of glaucoma: open-angle (which is the most
common form and affects approximately 95% of individuals) and
closed-angle. There are also several other varieties of glaucoma,
including secondary, normal-tension, congenital, pseudoexfoliation
syndrome, juvenile, neovascular, pigmentary, and irido-corneal-endothelial
syndrome (ICE syndrome).
Worldwide, it is estimated that about 66.8 million people have
visual impairment from glaucoma, with 6.7 million suffering from
blindness. In the United States, approximately 2.2 million people
age 40 and older have glaucoma, and of these, as many as 120,000 are
blind due the disease. The number of Americans with glaucoma is
estimated to increase to 3.3 million by the year 2020. Vision
experts estimate that half of those affected may not know they have
it because symptoms may not occur during the early stages of the
disease.
Glaucoma is a leading cause of blindness among African Americans and
Hispanics in the United States. African Americans experience
glaucoma at a rate of three times that of Caucasians and experience
blindness four times more frequently. Between the ages of 45 and 64,
glaucoma is fifteen times more likely to cause blindness in African
Americans than in Caucasians.
High-risk factors for open-angle glaucoma, the most common form of
the disease, include being an African American and over 40, having a
family history of the disease, and being over 60 for the general
population. Those who are very nearsighted, have a history of
diabetes, have experienced eye injury or eye surgery, or take
prescription steroids also have an increased risk of developing
glaucoma. It has also been suggested that individuals with Japanese
ancestry may be at a greater risk for normal-tension glaucoma, and
that those of Asian and Eskimo descent may have a greater risk for
closed-angle glaucoma.
Open-angle glaucoma, by far the most common form, has no symptoms at
first. At some point, side vision (peripheral vision) is lost and
without treatment, total blindness will occur.
Closed-angle glaucoma (acute glaucoma) results from a sudden,
complete blocking of the fluid flowing out of the eye. Symptoms may
include severe pain, nausea, vomiting, blurred vision, and seeing a
rainbow halo around lights. Closed-angle glaucoma is a medical
emergency and must be treated immediately or blindness could result
rapidly.
Currently, there is no "cure" for glaucoma; however, early diagnosis
and treatment can control glaucoma before vision loss or blindness
occurs.
There are several tests that can help your eye care professional
detect glaucoma; these include a visual acuity test, visual field
test, dilated eye exam, tonometry (which measures the pressure
inside of the eye), and pachymetry (which uses ultrasonic waves to
help determine cornea thickness). Individuals at high risk for
glaucoma should have a dilated pupil eye examination, and a
visual field test annually.
Early treatment for open-angle glaucoma will usually begin with
medications (pills, ointments, or eyedrops, for example) that either
help the eye to drain fluid more effectively or cause it to produce
less fluid. Several forms of laser surgery can also help fluid drain
from the eye. Incisional surgery to create a new opening for fluid
to drain is usually performed after the other treatment options have
failed.
When
a patient has glaucoma or is at high risk for developing the
disease, physicians may document how the optic nerve changes over
time by making drawings, taking photographs, or using a new
technique called optic nerve imaging. Scanning laser polarimetry (GDx),
confocal scanning laser ophthalmoscopy (Heidelberg Retinal Tomograph
or HRT III), and optical coherence tomography (OCT) are all examples
of optic nerve imaging techniques. The patient’s eye care
professional will make the determination as to which method(s) to
use.
New
research is focusing not only on lowering pressure inside the eye,
but is also exploring medications that will protect and preserve the
optic nerve from the damage that causes vision loss as well as the
role of genetic factors. There has been progress in understanding
the genetics of glaucoma in the last few years. Genes have been
found that are associated with congenital glaucoma, juvenile
glaucoma, normal-tension glaucoma, adult-onset open-angle glaucoma,
pigmentary glaucoma, and other conditions that are associated with
secondary glaucoma. |
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