glaucoma: gradual loss of peripheral vision, marked by blind
spots. Symptoms only develop at the later stages of the disease.
Screening exams are advised.
glaucoma: acute attacks involving severe eye pain, nausea
and vomiting, blurred vision, and the appearance of rainbow-colored
halos around lights.
When To Call Your Doctor
an ophthalmologist right away if you develop symptoms of
acute closed-angle glaucoma.
an ophthalmologist for a complete eye exam every two years
after age 50. (Those of African descent should start having
such exams at age 40.) People with a family history of glaucoma
should also have periodic exams.
What Is It?
Glaucoma is a sight-threatening disorder marked
by an increase in intraocular pressure (IOP), the pressure within
the eyeball. It occurs as a result of an excess buildup of aqueous
humorthe clear fluid inside the eyeball that provides nutrients
to and carries waste products away from the lens and cornea of
the eye, the only parts of the body with no blood supply. Each
day, the eye produces about one teaspoon of aqueous humor. Normally,
this fluid escapes from the eye through a spongy mesh of connective
tissue called the trabecular meshwork at the same rate at which
it is produced. In a common type of glaucoma, production of aqueous
humor appears to exceed the rate of its escape and the pressure
There are two forms of glaucoma: open angle and
closed angle. Open-angle glaucoma, which accounts for 90 percent
of all cases, is a slow, progressive disease that produces no
symptoms in its early stages. By contrast, closed-angle glaucoma
is relatively uncommon and is characterized by rapid and extreme
elevations of IOP, often causing acute symptoms such as severe
eye pain and rapid blurring of vision. Both types of glaucoma
may lead to blindness by damaging the optic nerve; however, early
detection and treatment can usually control IOP and prevent severe
vision loss. Most prevalent among those over age 40, glaucoma
is more common in African Americans or when there is a positive
What Causes It?
It is theorized
that open-angle glaucoma occurs when, for reasons not completely
understood, the trabecular meshwork becomes partially blocked.
IOP builds up as more aqueous humor is formed, but pressure doesnt
rise high enough to cause any noticeable symptoms initially.
When IOP remains elevated or continues to rise, however, fibers
in the optic nerve are compressed and destroyed, leading to a
gradual loss of vision over a period of years.
glaucoma is caused by a sudden blockage near the iris that prevents
aqueous humor from reaching the trabecular meshwork. The blockage
results in the rapid onset of extremely high IOP that may cause
severe, permanent vision loss within a day or two.
A family history
of visual-field loss due to glaucoma increases the risk of optic
nerve damage. Evidence also suggests that cardiovascular disease,
diabetes, and myopia (nearsightedness) increase the risk of nerve
damage from glaucoma.
is no way to prevent glaucoma, early detection and treatment
may prevent damage to the optic nerve. See an ophthalmologist
for a complete eye exam every two years after age 50. Those of
African descent should start having such exams at age 40.
Glaucoma is diagnosed by an eye examination which
emphasizes eye pressure measurement, viewing of the optic nerve,
and assessment of optic nerve function:
of an instrument to apply slight pressure upon the eyeball to
(in which the pupils are dilated with eye drops so that the optic
nerve may be magnified and examined with an ophthalmoscope, a
lighted viewing instrument).
(a visual-field test that determines the extent of peripheral
How To Treat It
a chronic disorder that cannot be cured. Open-angle glaucoma
can often be treated safely and effectively by medical or surgical
measures, though lifelong therapy is almost always necessary.
Medications are nearly always used first. However, laser surgery
is becoming a more common first option.
Eye drops are
the most frequent medical treatment for glaucoma because they
have fewer overall side effects than oral medications. Depending
on the type, eye drops must be applied one to four times a day,
regularly and on schedule, to maximize IOP control. Five types
of eye drops are currently used: miotics (such as pilocarpine),
beta-blockers (like timolol or levobunolol), adrenergic agonists
(such as epinephrine or dipivefrin), topical prostaglandins (latanoprost),
and carbonic anhydrase inhibitors (dorzolamide). Miotics (drugs
that constrict the pupil) and adrenergic agonists increase the
outflow of aqueous humor. Beta-blockers diminish the production
of aqueous humor. Latanoprost, the newest type of glaucoma eyedrop,
reduces IOP by increasing the outflow of aqueous humor. Because
it works differently than other glaucoma drugs, it can be used
along with a second medication to reduce IOP further. Dorzolamide
drops, previously available only as tablets, decrease production
of aqueous humor.
inhibitor pills are generally used when optic nerve damage continues
or seems highly likely despite maximal topical treatment. These
oral medications initially lower IOP by 20 to 30 percent on average,
but significant systemic side effects (such as numbness or tingling
in the extremities, malaise, and loss of appetite) and occasional
serious complications (such as kidney stones, depression, diarrhea,
and blood abnormalities) can limit their use.
examinations are essential throughout medical therapy. These
may initially be required daily or weekly for those with severe
nerve damage or extreme elevations of IOP, or only every three
to six months for patients with stable IOP and minimal optic
successful more often than medical treatment. However, it carries
a greater risk of complications, including the development of
cataracts, and repeat procedures may be required. About 10 percent
of those with open-angle glaucoma require surgery, when drug
therapy fails or when the patient has a medical condition (such
as hypertension or severe heart or lung disease) that precludes
maximal drug therapy. The two most common surgical procedureslaser
trabecular surgery and filtration surgeryreduce ocular
pressure by opening a passage for aqueous humor.
IOP is relieved promptly during an acute attack of closed-angle
glaucoma, blindness can occur within a day or two. Making a hole
in the iris (iridotomy) creates a drainage path for the aqueous
humor. Iridotomy in the other eye is generally recommended owing
to the high likelihood that it will be involved in a future acute
attack. The procedure can usually be performed with a laser.
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