|
Glaucoma: The Second-Leading Cause
of Blindness in the U.S.A
By Judith Lee and Gretchyn Bailey; reviewed by Dr. Vance
Thompson
Glaucoma:
Your eye has pressure just like your blood, and when this intraocular pressure (IOP)
increases to dangerous levels, it damages the optic nerve. This can result in
decreased peripheral vision and, eventually, blindness. Glaucoma is similar to
ocular hypertension but with accompanying optic nerve damage and vision loss.
Glaucoma affects an estimated 3 million Americans, with 120,000 blind due to the
condition. Elsewhere in the world, glaucoma treatment is less available, and
glaucoma ranks as a leading cause of blindness just about everywhere. Even if
people with glaucoma do not become blind, vision can be severely impaired.
There are two major types of glaucoma: chronic or primary open-angle glaucoma (POAG)
and acute closed-angle glaucoma. Other variations include congenital glaucoma,
pigmentary glaucoma and secondary glaucoma.
Glaucoma Signs and Symptoms:
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.
Glaucoma gradually reduces your peripheral vision, but by the time you notice
it, permanent damage has already occurred. If your IOP remains high, the
destruction can progress until tunnel vision develops, and you will only be able
to see objects that are straight ahead.
What's your glaucoma risk?
An acute attack of narrow-angle glaucoma, also termed acute angle-closure
glaucoma or acute closed-angle 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.
Other signs include headaches, blurred vision, difficulty adapting to darkness,
or haloes around lights. Chronic glaucoma normally develops after age 35.
Like POAG, normal-tension glaucoma (also termed normal-pressure glaucoma,
low-tension glaucoma or low-pressure glaucoma) is an open-angle type of glaucoma
that can cause visual field loss due to optic nerve damage, but in
normal-tension glaucoma, the eye's IOP remains in the normal range.
Chronic narrow-angle glaucoma, like open-angle glaucoma, can be symptomless
until vision loss occurs.
Open angle glaucoma is one of the most common forms of the disease. See
animation.
Acute angle-closure glaucoma is a medical emergency. If the high pressure is not
reduced within hours, it can permanently damage vision. Anyone who experiences
its symptoms should immediately contact an ophthalmologist or go to a hospital
emergency room.
It's difficult to spot signs for congenital glaucoma because the children are
too young to understand. If you notice a cloudy, white, hazy, enlarged or
protruding eye, consult your eye doctor. Congenital glaucoma occurs more in boys
than girls.
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.
Symptoms of chronic glaucoma following an eye injury could indicate secondary
glaucoma.
What Causes Glaucoma?
An increased IOP reading indicates a problem with the amount of aqueous humor
(fluid) in the eye: either the eye is producing too much, or it's not draining
properly. The drainage area is the angle formed between the cornea and the iris,
which is why you see the word "angle" in the different glaucoma names.
In chronic glaucoma, the aqueous humor can't make it through meshwork in the eye
to the drainage channel. Risk factors for this type of glaucoma include:
Age. In a major study, less than 1% of people age 60 to 64 had chronic
open-angle glaucoma. Among people 10 years older, the prevalence more than
doubled to 1.3%, and among those 80 to 84, it more than doubled again to 3%.
Certain medical disorders. Diabetes, extreme nearsightedness and previous eye
surgery are risk factors for chronic open-angle glaucoma. Additionally, if you
have a condition that requires the use of oral or inhaled steroids, particularly
high doses for prolonged periods, that can increase your risk as well.
Ethnic background. Chronic glaucoma is four times more common in
African-Americans than in whites. It also develops earlier: African-American
risk starts to increase after age 45, white risk at age 60. Among whites, groups
at higher risk include people with Scandinavian, Irish and Russian backgrounds.
Family history. Like so many diseases, glaucoma tends to run in families;
different genes, however, are involved in different families.
The cause of normal-tension glaucoma is not known, but many doctors believe it
is related to poor blood flow to the optic nerve. Normal-tension glaucoma is
more common in those who have a history of vascular disease, are Japanese or are
female.
Narrow-angle glaucoma occurs in less than 10% of glaucoma patients. In this form
of the disease, aqueous humor cannot drain out of the eye due to very narrow
drainage angles that are usually blocked by the iris. This condition can occur
slowly and progressively, or very quickly.
Are your eyes irritated from looking at a computer all day? Try these tips:
1. Use eyedrops to lubricate your eyes.
2. Take several breaks per hour.
3. Position your monitor so that room windows are to the side, not the front or
back.
Again, rapid closing of the angles, or acute angle-closure glaucoma, is a
medical emergency. Optic nerve damage and vision loss will occur within hours if
the angles are not opened to drain fluid and lower IOP. Acute angle-closure
glaucoma may be triggered by anything dilating the pupil, resulting in more of
the iris blocking the angles. Dim lighting, drops administered by your eyecare
practitioner during an eye examination, or certain medications such as
antihistamine/decongestant drops or cold medications may cause an acute
angle-closure attack.
Congenital glaucoma is a rare form of the disease affecting babies, with
80% of cases diagnosed by age one. These children are born with narrow angles or
some other defect in the drainage system of the eye.
Pigmentary glaucoma, another rare form of the disease, is caused by
pigment from the iris clogging the draining angles, preventing aqueous humor
from leaving the eye. Over time, the inflammatory response to the blocked angle
damages the drainage system.
Secondary glaucoma develops after trauma to the eye that affects the
drainage system. Injury, infection, inflammation, tumor or an enlarged cataract
can precipitate secondary glaucoma.
Glaucoma Treatment:
The best way to prevent vision loss from glaucoma is early diagnosis and
treatment. See your eyecare practitioner at least every two years for a complete
examination, including an IOP check. People at high risk for glaucoma due to
high intraocular pressures, family history, ethnic background, age or optic
nerve appearance may need more frequent visits to the eye doctor.
A test called a visual field may be performed on glaucoma suspects to detect
peripheral vision loss. It involves staring straight ahead into a machine and
clicking a button when you notice a blinking light in your peripheral vision.
The visual field test may be repeated at regular intervals for your doctor to
determine the extent of vision loss.
Glaucoma treatment (for any form) entails decreasing aqueous humor production,
increasing fluid drainage or a combination of the two. These treatments will not
restore any vision already lost to glaucoma.
Glaucoma can be very destructive to your vision; in fact, it's the
second-leading cause of blindness in the U.S.
Generally the first stage of glaucoma treatment is beta-blocker eyedrops, which
will lower fluid production in the eye. These may not be used in people with
heart conditions, because they can affect heart or lung function. There are
other pressure-lowering drops besides beta-blockers that are known as alpha-2
agonists and prostaglandin analogs. Many of the drugs used for glaucoma interact
with common medications. Patients should discuss these issues with both the
family physician and the eyecare practitioner.
Most cases of glaucoma can be controlled with a single drug or drug
combinations, but some patients may require or select surgery. About 70% of
patients need new or extra medications within two years after the start of drug
treatment. That's compared with 56% of those who choose laser surgery.
During a type of glaucoma surgery called trabeculoplasty, the doctor uses a
laser to create tiny holes where the cornea and iris meet, to increase aqueous
humor drainage. Another procedure called trabeculectomy creates an artificial
drainage area; it's used in cases of advanced glaucoma where there is optic
nerve damage and the IOP continues to soar. A third option is a drainage device,
which the surgeon implants in your eye to improve fluid drainage.
Marijuana for Glaucoma: Does It Work?
Some people with glaucoma use marijuana because research has found that it has a
small effect in lowering intraocular pressure. However, no research has found
that marijuana is anywhere near as effective as legal glaucoma medications, and
the American Academy of Ophthalmology, among others, says the risky side effects
of marijuana far outweigh any benefit. People who use marijuana instead of their
prescribed glaucoma medication run the risk of losing their vision.
Frequently asked questions
1. What exactly is glaucoma?
Glaucoma is a condition in which the eye's intraocular pressure (IOP) is too
high. This means that your eye has too much aqueous humor in it, either because
it produced too much, or because it's not draining properly. Other symptoms are
optic nerve damage and vision loss.
2. What's the difference between glaucoma and ocular hypertension?
Ocular hypertension is another term for high IOP; the pressure is not high
enough to cause optic nerve damage and vision loss.
3. Why does my eye doctor want to do more than one kind of glaucoma test?
The "puff test" that most people are familiar with measures IOP. Another way
doctors may measure it is by pressing an instrument called an applanation
tonometer against your eye to determine how much resistance there is.
Your doctor may also want to check for optic nerve damage by dilating your eyes,
or to check for vision loss with a visual field test.
4. Who's at the most risk for glaucoma?
If you're over age 60, African-American, diabetic or have a family member with
glaucoma, you are at higher risk for glaucoma than others.
5. Is there any way to prevent glaucoma?
Doctors don't know of any way to prevent glaucoma. Dr. Burt Dubow, optometrist
and AllAboutVision.com board member, said, "Current research is suggesting that
optic nerve nutrition can be enhanced with certain drugs and also with certain
nutritional agents, like gingko biloba."
"My suggestion would be to avoid smoking and excessive alcohol, eat a healthy
diet, keep your weight down, exercise, take nutritional products and be sure to
see your eye specialist on a regular basis."
6. What are the signs and symptoms of glaucoma?
There are usually no signs that you're developing glaucoma until vision loss
occurs, which is why it's so important to have regular eye exams. Your eye
doctor can diagnose and treat high IOP before it progresses to optic nerve
damage and vision loss.
7. What are the different types of glaucoma?
Primary open-angle glaucoma (POAG) is the most common form of glaucoma. The
other types are: normal-tension, narrow-angle, closed-angle, congenital,
pigmentary and secondary. Detailed descriptions of each type are available in
our Glaucoma article.
8. Is glaucoma curable?
No, but it's important to treat glaucoma, because it can cause blindness.
9. What glaucoma treatments are currently available?
Doctors usually prescribe special eyedrops that reduce intraocular pressure.
These are used one or several times a day, depending on the medication. If the
drops don't work, surgery may be the next step. Treatment details are available
in our Glaucoma article.
|
