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Glaucoma
Glaucoma is the second leading cause of loss of vision in the United
States today, affecting over three million Americans. Few patients with
glaucoma lose their sight completely, thanks to earlier detection and the
development of better treatments.
What is Glaucoma?
Glaucoma is a term used to describe an abnormally high amount of pressure
within the eyeball that causes damage to the optic nerve. Glaucoma refers
to a group of diseases, all of which cause increased pressure within the
eyeball (intraocular pressure). The optic nerve serves to carry images
from the retina to the brain. As the optic nerve deteriorates, blind spots
begin to develop in the visual field, starting from peripheral vision
(side).
The internal pressure within the eye enables the eye to maintain its shape
and function. Increased pressure interferes with the normal shape of the
eye, causing damage to the optic nerve. Normal pressure within the eye is
maintained through vitreous fluids present in the vitreous cavity at the
back of the eye, and the aqueous humor at the front of the eye. The
continuous flow of fluid from the back of the eye and drained through the
front of the eye is what maintains normal pressure, providing constant
nourishment of the cornea and lens. To maintain normal pressure, aqueous
humor must be produced at the same rate as it is drained.
The drainage system must function properly for the eye to maintain normal
pressure. When it doesn't, and the drainage is blocked, increased eye
pressure causes damage to the fibers that constitute the optic nerve.
Many people have glaucoma and don't know it. Glaucoma typically develops
over time, impacting sight before a patient is aware of it. If left
untreated, glaucoma can lead to complete vision loss. However, when
detected early, glaucoma can be successfully treated and cause very minor
vision loss. There is no cure for glaucoma, and patients require continual
treatment throughout their life.
Different types of glaucoma result from the causes of internal eye
pressure.
There are two main types of glaucoma. Both of these types of glaucoma can
be either primary, meaning that the cause is unknown, or secondary, which
refers to a known cause, such as eye injury or disease.
Primary open-angle glaucoma typically affects both eyes. Initial symptoms,
such as light sensitivity, difficulty differentiating between light and
dark shades, and problems with vision at night, may occur only in one eye.
This type of glaucoma typically progresses with few symptoms until it
reaches an advanced stage, damaging the optic nerve as it progresses and
causing a reduction in peripheral vision.
Acute angle-closure glaucoma can cause severe symptoms due to its sudden
development. It is caused by a fast, significant rise in eye pressure and
immediate medical attention is required. Without fast intervention, sudden
and significant vision loss can occur. Symptoms of a sudden attack
include; headache, intense eye pain, nausea, blurred vision, reddening of
the eyes, hardness of the eye(s), and the presence of halos around lights.
Are you at risk?
Predicting who will and who will not develop glaucoma is difficult.
Although increased intraocular pressure increases the risk of developing
glaucoma, most people with increased intraocular pressure do not develop
glaucoma.
There are, however, some factors that increase a person's risk of
developing glaucoma.
1) Family History
Patient's with one parent who has glaucoma have a 20% chance of developing
the disease, whereas patient's with one sibling with glaucoma have a 50%
chance of developing the disease.
2) Age
Glaucoma is rare in people under age 40. Beginning at age 50, the risk of
developing glaucoma doubles every 10 years.
3) Race
Researchers are unclear about the reasons why, but American blacks are up
to 4 times more likely to develop glaucoma than are American whites. Asian
Americans and Japanese Americans are more likely to develop some types of
glaucoma than others.
4) Injury
Physical injury to the eye can result in an increased chance of developing
glaucoma.
5) Medical Conditions
Patient's with diabetes are almost 3 times more likely to develop glaucoma
than those without diabetes. High blood pressure, heart disease, eye
tumors and inflammations and retinal detachment can increase the chance of
developing glaucoma.
6) Nearsightedness
Nearsighted individuals are 2-3 times more likely to develop glaucoma.
7) Corticosteroid Use
The risk of developing secondary glaucoma increases with prolonged use of
corticosteroids.
Diagnosing Glaucoma
Several tests are available to help a doctor diagnose glaucoma in a
patient.
1) Tonometry
This is a simple test that measures a patient's intraocular pressure.
People with an intraocular pressure over 30 mm Hg are at increased risk
for developing glaucoma.
2) Optic Nerve Damage Tests
Using an ophthalmoscope, a doctor can look through the pupil to the back
of the eye to assess the condition of optic nerve fibers.
3) Visual Field Tests
These tests enable a doctor to map the visual field of patient, thereby
showing limitations in peripheral vision.
4) Gonioscopy & Tonography
These tests help a doctor distinguish whether glaucoma is open-angle
glaucoma or angle-closure glaucoma.
Typically, a doctor will perform a number of tests before diagnosing
glaucoma. A doctor will determine whether several factors associated with
glaucoma are present, including increased intraocular pressure, damage to
the optic nerve and areas of vision loss.
Glaucoma can be successfully managed and treated if diagnosed early. This
is just one of many reasons why annual
eye exams are important.
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Resources: Learn about breaking new
developments in
glaucoma research. Comprehensive coverage
about glaucoma accessible to the visually
impaired. |
