Glaucoma is a group of diseases that can damage the eye's optic nerve
and result in vision loss and blindness. Early treatment is important to prevent serious vision loss.
There are 5 types of glaucoma:
Open-angle glaucoma. This is the most common type. It is
characterized by slowly increasing eye pressure and the gradual loss of
side vision. In medical term, eye pressure is called intraocular pressure
(IOP). It is the fluid pressure inside the eye.
Low-tension or normal-tension glaucoma. The optic nerve is damaged but
the eye pressure is normal.
Closed-angle glaucoma. This type produces a sudden increase in eye
pressure. Symptoms include severe pain and nausea, as well as redness of
the eye and blurred vision. This is a medical emergency and requires
immediate treatment. Without treatment, blindness may occur in 1 or 2
Congenital glaucoma. This type affects children who are born with
eye defects that slows the normal drainage of fluid. These children
usually have obvious symptoms, such as cloudy eyes, sensitivity to light,
and excessive tearing.
Secondary glaucoma. This type develops as a complication of other
medical conditions. It may be associated with
eye surgery or advanced cataracts, eye injuries, certain eye tumors, or
uveitis (eye inflammation). Pigmentary glaucoma occurs when pigment
from the iris flakes off and blocks the meshwork, slowing fluid drainage.
A severe form, called neovascular glaucoma, is linked to diabetes.
Corticosteroid drugs used to treat eye inflammations and other diseases
can trigger glaucoma in some people.
The following is focused on open-angle glaucoma.
Symptoms and Diagnosis
At first, there are no symptoms. Vision stays normal, and there is no pain.
However, as the disease progresses, a person with glaucoma may notice his
or her side vision gradually failing. That is, objects in front may still be
seen clearly, but objects to the side may be missed.
As glaucoma remains untreated, people may miss objects to the side and out
of the corner of their eye. Without treatment, people with glaucoma will
slowly lose their peripheral (side) vision. They seem to be looking through a
tunnel. Over time, straight-ahead vision may decrease until no vision remains.
Glaucoma can develop in one or both eyes.
By a person with glaucoma
Glaucoma is detected through a comprehensive eye exam that includes:
- Visual acuity test. This eye chart test measures how well you see
at various distances.
- Visual field test. This test measures your side (peripheral)
vision. It helps your eye care professional tell if you have lost side
vision, a sign of glaucoma.
- Dilated eye exam. Pupil dilation provides eye care professional
with a better view of the optic nerve to check for signs of damage. Drops are placed in your eyes to widen, or
dilate, the pupils. After the exam, your close-up vision may remain blurred for
- Tonometry. The procedure to determine the IOP. There are many
types of tonometry. The simplest but not very accurate type is called
noncontact (or air-puff) tonometry which is often used to screen for high
- Pachymetry. A numbing drop is applied to your eye. Your eye care
professional uses an ultrasonic wave instrument to measure the thickness
of your cornea.
In the front of the eye is a space called the anterior chamber. A clear
fluid flows continuously in and out of the chamber and nourishes nearby
tissues. The fluid leaves the chamber at the open angle where the cornea and
iris meet. When the fluid reaches the angle, it flows
through a spongy meshwork, like a drain, and leaves the eye.
Sometimes, when the fluid reaches the angle, it passes too slowly through
the meshwork drain. As the fluid builds up, the pressure inside the eye rises
to a level that may damage the optic nerve. When the optic nerve is damaged
from increased pressure, open-angle glaucoma--and vision loss--may result.
That's why controlling pressure inside the eye is important.
National Eye Institute, USA.