Glaucoma

Basics

This review will focus on the most common type of glaucoma,
primary open-angle glaucoma (POAG). The 3 other types of glaucoma are:
acute angle-closure glaucoma, secondary glaucoma, and congenital
glaucoma. Glaucoma causes decreased vision and can lead to blindness by
damaging the optic nerve—the major nerve in the eye that controls
vision.

Glaucoma is the top cause of irreversible blindness in the world.
In 2000, researchers estimate that more than 2 million Americans had
POAG. In the same year, researchers also estimated that more than
130,000 people in the U.S. had become blind due to POAG.

POAG is the most common cause of irreversible blindness among
African Americans. Glaucoma usually damages your eyes slowly, over many
years. You may not know you have glaucoma until your vision has been
irreversible damaged. Getting regular tests for glaucoma by your eye
doctor can help prevent this kind of damage.

Causes

The exact cause of POAG is not known. POAG occurs when eye fluid,
known as aqueous humor, backs up in your eye. Doctors and researchers do
not know exactly why the fluid backs up, but it may be due to poor
drainage of the fluid. When the aqueous humor builds up in your eye, the
extra pressure can damage the optic nerve, damaging your vision.

Symptoms

Most people with POAG do not develop symptoms. POAG only causes
symptoms when the disease is very advanced. If you have advanced POAG,
you may start to lose your peripheral vision. But, you can have
long-standing glaucoma without feeling any discomfort.

Risk Factors

Diagnosis

Your doctor will diagnose you with glaucoma if you meet certain
conditions. By looking in the back of your eye, known as your fundus, your
primary care doctor may notice changes in your eye disk, called cupping. If
he or she sees this on office exam, you should be referred to an eye doctor.

You might be diagnosed with increased IOP in a community-based
screening or if you are having your eyes checked while you buy new glasses.
Having increased IOP does not necessarily mean you have POAG, but you should
be referred for a complete exam by an eye doctor.

Several tests are available to determine if you have increased IOP.
These include the Schiotz method, in which your eye doctor will numb your
eye then press a tonometer next to your eye to measure the pressure. Your
doctor may put an orange dye in your eye and then measure the pressure while
taking a close look at your eye with a slit-lamp. This is called the
aplanation method. The puff test may also be used. This technique can
measure your IOP by blowing a tiny amount of air into your eye, and
measuring the force needed to indent your eye. Normal eye pressures range
from 10 to 20 mmHg. If your pressure is higher than that, your doctor will
probably perform additional tests.

If you have increased IOP, your eye doctor will check the thickness
of your cornea, using tachymetry. To perform this test, your doctor will
numb your eye with drops and then use an ultrasound machine to measure how
thick your cornea is. If your cornea is thin, you have a higher risk of
developing POAG.

If these tests suggest you could have glaucoma, you will be closely
examined for optic nerve damage. Your doctor will use an ophthalmoscope or
bioscope to look directly into your eye; he/she may take pictures using a
computer and special camera to closely examine your optic nerve.

It is important for you to take all the medications your doctor
prescribes, keep your appointments, and notify your doctor if your
vision begins to worsen.

Ask your doctor about medicine you can take by mouth to help
treat glaucoma.

If eye drops and pills are not effective in treating your
glaucoma, your eye doctor may recommend a type of surgery called a
trabeculectomy, or a filtering procedure. Trabeculectomy would open up
passages in your eye to improve the flow of aqueous humor. You would
receive antibiotic eye drops following the procedure and go back to see
your eye doctor for follow up. You may need to have this procedure
repeated a few times for the pressure in your eye to really improve. A
trabeculectomy will not improve your vision, but it can help prevent
your vision from getting worse.

There are no known alternative medicine treatments for glaucoma.

Laser therapy can also be an effective treatment for POAG. Your
eye doctor can do this quick procedure in the office. This procedure
allows more of the eye fluid to drain.

Many people with glaucoma take prescription eye drops. You can
ask your doctor about which eye drops would be best for you.

Screening for glaucoma can help prevent severe visual loss, but
not all medical societies agree on how often to screen people. The
American Academy of Ophthalmology recommends that everyone over age 40
have a full eye exam and a test for IOP. If you are not at high risk for
glaucoma, you should have a repeat screening exam every 3 to 5 years. If
you have a higher risk for glaucoma and/or you are over the age of 60,
you should get a screening exam every 1 to 2 years.

Childhood glaucoma is a rare condition that occurs in infants and
babies within their first year. Children with this condition may have
sensitivity to light and a cloudy cornea. Early diagnosis and treatment
can help babies and children retain normal vision.

Prevention and Screening

Treatment