Glaucoma is the diagnosis given to a group of ocular conditions that contribute to the loss
of retinal nerve fibers with a corresponding loss of vision. Glaucoma therefore is a disease
of the optic nerve, the nerve bundle which carries the images we see to the brain.
The eyeball is basically a rigid sphere filled with fluid. As the total amount of fluid within the
eye increases, so does the pressure, similar to over inflating a tire. Many people know that
glaucoma has something to do with pressure inside the eye. The higher the pressure inside
the eye, the greater the chance of damage to the optic nerve. Glaucoma is said to be the
leading cause of blindness in people over the age of 40 and it affects approximately 2% of
that population. The visual defect is most often observed as enlargement of the physiological
blind spot and other visual field losses. However, if detected early, complete blindness
resulting from glaucoma can be prevented.
Glaucoma is most common in people with a family history of the disease, and in nearsighted
patients. Patients with systemic diseases such as diabetes, anemia, or hardening of the
arteries are at a higher risk of developing glaucoma. African-Americans tend to develop
glaucoma more often than other racial groups. A comprehensive eye examination is
required for diagnosis, and early treatment is the best way to preserve vision once the
diagnosis has been made.
What Causes Glaucoma?
The front portion of the eye is filled with a nourishing, protective fluid called
aqueous humor. This transparent fluid is continuously circulated through the
inner eye , flowing in and draining out, much like a sink with the faucet turned
on all of the time. If the "drainpipe" gets clogged, water collects in the sink and
pressure builds up. If the drainage area of the eye called the drainage angle is
blocked, the fluid pressure within the inner eye may increase, which can
damage the optic nerve - the part of the eye responsible for transforming the
images we see into impulses the brain can translate. This damage can result in
partial or complete blindness.
Common Types of Glaucoma
Open Angle Glaucoma
The most common type of glaucoma, known as chronic open angle/primary open angle,
occurs when the canals draining the eye of aqueous humor become clogged. This blockage
gradually increases pressure within the eye. Individuals are usually unaware of changes
occurring within the eye. As a result, periodic eye examinations are the best method for
early detection of glaucoma. Over 90% of adult glaucoma patients have this type of
glaucoma.
Closed Angle Glaucoma
When eye pressure builds up rapidly, it is called acute angle-closure glaucoma. This type
of glaucoma commonly occurs in individuals who have narrow anterior chamber angles. In
these cases, aqueous fluid behind the iris cannot pass through the pupil and pushes the iris
forward, preventing aqueous drainage through the angle. Is as though a sheet of paper
floating near a drain suddenly drops over the opening and blocks the flow out of the sink.
In cases of acute angle closure glaucoma, one may experience blurred vision, halos around
lights, pain, nausea, and vomiting. If you have any of these symptoms, call your
ophthalmologist immediately. If pressure within the eye is not immediately relieved,
blindness may result in a matter of days.
Secondary Glaucoma occurs from inflammation, degeneration, trauma, or tumor growth
within the eye. Certain medications are also said to cause secondary glaucoma.
How Is Glaucoma Detected?
Measuring the pressure within the eye by itself does not give us a diagnosis of glaucoma. Of
more importance is the direct observation of damage to the optic nerve itself and sometimes
the nerve fiber layer of the retina. Quantifying a loss of vision in part of the visual field
consistent with observed nerve fiber loss is the true definitive diagnosis for glaucoma.
There are several tests which the ophthalmologist may perform to confirm a diagnosis of
glaucoma. Since a large percentage of glaucoma sufferers do indeed have elevated intraocular
pressure, careful measurement of the eye pressure on a regular basis (for high risk people)
is a crucial step in early detection. This pressure is measured using an instrument called a
tonometer. The back of the eye is also observed through an ophthalmoscope to make sure that
the optic nerve is healthy. The drainage angle of the eye is also inspected with a special type of
“contact lens” (gonioscopy). The ophthalmologist may also choose to test the patient's side
vision (perimetry/visual field). Some of these tests may not be necessary for every person,
and others may need to repeat these tests on a regular basis, to determine if glaucoma
damage is increasing over time.
Who is at risk for glaucoma?
High pressure alone does not mean that you have glaucoma. Your ophthalmologists puts
together many kinds of information to determine your risk for developing the disease. The
most important risk factors include: Age, near-sightedness, African ancestry, a family history
of glaucoma, past injuries to the eyes:; a history of severe anemia or shock. Your
ophthalmologist will weight all of these factors before deciding whether you need treatment
for glaucoma, or whether you should be monitored closely as a glaucoma suspect. This
means your risk of developing glaucoma is higher than normal, and you need to have
regular examinations to detect the early signs of damage to the optic nerve.
How is glaucoma treated?
As a rule, damage caused by glaucoma cannot be reversed. Therefore, the goal in the
management of glaucoma is to reduce the intraocular pressure to the point whereby the
remaining healthy nerve fibers are able to receive proper nourishment and therefore
maintain function.
Eyedrops
Glaucoma is usually controlled with eye drops taken several times a day, sometimes in
combination with pills. These medications are used to prevent damage to the optic nerve
by decrease eye pressure, either by slowing the production of aqueous fluid within the eye
or by improving the flow leaving the drainage angle. Recently there have been a few brand
new medications which show great promise for more effectively and conveniently
managing glaucoma.
It is important to tell all of your doctors about the eye medications that you are using for
glaucoma control. In order for these medications to work, you must take them regularly and
continuously as they were prescribed. Quite simply, the key to the success of medication
therapy is patient compliance.
Laser surgery
If topical and/or oral therapy is not controlling the intraocular pressure (IOP), or if the
patient is not taking their medicine according to schedule, laser surgery treatment may be
an effective alternative or adjunct. The laser is usually used in one of two ways. In
open-angle glaucoma, the laser is used to enlarge the drain (argon laser trabeculoplasty)
to help control eye pressure. In angle-closure glaucoma, the laser creates a hole in the iris
(iridotomy) to improve the flow of aqueous fluid to the drain.
Operative surgery
When operative surgery is needed to control glaucoma, your ophthalmologist creates a new
drainage channel (bleb) through which the aqueous fluid can leave the eye, thereby
lowering the IOP.
Fortunately, technology has improved significantly for both the medication and laser
treatment alternatives in glaucoma, so that only a very few individuals need ever progress to
the point of needing surgery. The key to a lot of these successes however, lie in prevention;
specifically, the earlier that glaucoma can be diagnosed, the more effective the treatment
through either medications or laser.
Patient responsibility
Treatment for glaucoma requires a "team" made up of both you and your doctor. Your
ophthalmologist can prescribe treatment for glaucoma, but only you can make sure you
take your eye drops or pills. Never stop taking or change your medications without first
consulting your ophthalmologist.
Periodic eye examinations and tests are critical to monitor your eyes for any changes
because glaucoma can worsen without your being aware of it. Your ophthalmologist will
schedule frequent short exams in which they will monitor the pressure within the eye.
Remember, regular medical eye exams may help prevent unnecessary vision loss.
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