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 Glaucoma
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GLAUCOMA THE SECOND LEADING CAUSE OF BLINDNESS IN THE U.S.
It is estimated that there are more than 2 million people with
glaucoma and 70 million worldwide. Glaucoma is a group of eye disease
characterized by increased intraocular pressure (fluid pressure within the eye)
or IOP resulting in damage to the optic nerve and retinal nerve fibers.
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This nerve is like an electric cable. It contains a million
wires, each carrying a message to the brain, which joins together to provide
side vision as well as sharp central reading vision. Glaucoma can produce
damage to these "wires", causing blind sports in areas of vision to
develop. Unfortunately, people seldom notice these blind areas in the
side vision until considerable optic nerve damage has occurred. If the
entire nerve is destroyed, blindness results. However, when diagnosed and
treated early, blindness from glaucoma is almost always preventable.
There are two major types of glaucoma:
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Chronic or primary open-angle glaucoma (POAG).
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Closed-angle glaucoma.
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Other variations include congenital glaucoma, pigmentary glaucoma,
and secondary glaucoma.
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| Open-Angle
Glaucoma |
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Chronic glaucoma (primary open-angle glaucoma
or POAG) is often called "the silent thief of sight" because you have no
warning sign, no hint that anything is wrong. About half of Americans
with chronic glaucoma don't know they have it. The eye receives its
nourishment from a clear fluid that circulates inside the eye. This fluid
must be constantly returned to the blood stream by the eye's drainage canal,
called the trabecular meshwork. In the case of open-angle glaucoma,
something has gone wrong with the drainage canal. When the fluid
cannot drain fast enough, pressure inside the eye begins to build. This
excess fluid pressure pushes against the delicate optic
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nerve. If the pressure remains too high for too long,
irreversible vision loss can occur.
Symptoms of open-angle glaucoma:
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In early stages, there are no symptons. There is no pain or
outward sign of trouble.
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Mild aching in the eyes.
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Gradual loss of peripheral vision (the top, sides and bottom areas
of vision).
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Seeing halos around lights.
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Reduced visual acuity (especially at night, that is not correctable
with glasses).
Diagnosing open-angle glaucoma
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Your doctor will use tonometry
to check your eye pressure. After applying numbing drops, the tonometer
is gently pressed against the eye and its resistance is measured and
recorded. An opthalmoscope can be used to examine the
shape and color of your optic
nerve. |
| The ophthalmoscope
magnifies and lights up the inside of the eye. If the optic nerve appears
to be cupped or is not a healthy pink color, additional test will be run.
Perimetry (or visual field examination) is a
tests that maps the field of vision. Looking straight ahead into a white
bowl-shaped area, you'll indicate when you're able to detect lights as they are
brought into your field of vision. This map allows your doctor to see any
pattern of visual changes caused by early stages |
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| of glaucoma. Gonioscopy is used
to check whether the angle where the iris meets the cornea is open or
closed. This helps your doctor determine if they are dealing with
open-angle glaucoma or closed-angle glaucoma. |
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| Treating open-angle glaucoma |
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| To control glaucoma, your doctor may use medicines,
laser surgery and/or filtration surgery. Medicines may
come in pill or eye drop form. They work by either slowing the production
of fluid within the eye or by improving the flow through the meshwork.
Laser Trabeculoplasty surgery treats the drainage canal.
Requiring only numbing drops, the laser beam is applied to the trabecular
meshwork resulting in an improved rate of drainage. Filtration
surgery is performed when medicines and/or laser surgery are
unsuccessful in controlling eye pressure. During this microsopic
procedure, a new drainage channel is created to allow fluid to drain from the
eye. |
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| Closed-Angle
Glaucoma |
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| Closed-angle glaucoma is much more rare
and is very different from open-angle glaucoma. An accute attack of
closed-angle glaucoma, also termed acute angle-closure glaucoma,
produces sudden symptoms such as eye pain, headaches, haloes around lights,
dilated pupils, vision loss, red eyes, nausea and vomiting. These signs
may last for a few hours, then return again for another round. Each
attack takes with it part of your field of vision. If not treated
promptly, the glaucoma in the eye (IOP) usually goes up very fast when the
drainage canals get blocked or covered over. The iris gets pushed against
the lens of the eye, shutting off the drainage angle. Sometimes the lens
and the iris stick to each other. This results in pressure
increasing suddenly, usually in one eye. Because of the rapid potentially
devastating results of closed-angle glaucoma, you should seek medical treatment
immediately if you experience any of the above symptoms. |
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| Normal visual field |
Paritally diminished visual
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| Diagnosing and treating closed-angle glaucoma |
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| Diagnosing closed-angle glaucoma is done much like that
of open-angle galucoma. (See diagnosing open-angle glaucoma.)
Laser iridotomy is a common treatment for closed-angle
galucoma. During this procedure, a laser is used to create a small hole
in the iris, restoring the flow of fluid to the front of the eye. In most
patients, the iridotomy is placed in the upper portion of the iris, under the
upper eyelid, where it cannot be seen. Filtration surgery
is performed when medicines and/or or laser surgery are unsuccessful in
conrtrolling eye pressure. During this microscopic procedure, a new
drainage channel is created to allow fluid to drain from the eye. |
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| Other
Tyeps of Glaucoma |
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| It's difficult to spot signs for congential glaucoma
because children are too young to understand. If you notice a
cloudy, white, hazy, enlarged or protruding eye, consult your eye doctor.
Congential glaucoma occurs more often in boys than in girls. |
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| Pigmentary glaucoma often exhibits no
symptoms at all. You may notice some pain and blurry vision after
exercise. Pigmentary glaucoma affects mostly white males in their mid-30s
to mid-40s. |
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| Symptoms of chronic glaucoma following an eye injury
could indicate secondary glaucoma. |
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