All forms of
glaucoma cause the same characteristic changes in the
optic nerve, at the back of the eye, and the nerve fibers. Glaucoma causes
changes in the appearance of the
optic disc (notching or thinning of the edge) and
changes in the nerve fiber layer (fiber defects). Tiny amounts of bleeding
(hemorrhages) near the optic disc may represent ongoing damage from the
Other findings are used to determine how bad the disease is.
Doctors classify the severity of glaucoma in the following
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Important: Your doctor is your first...
Ocular hypertension is consistently elevated
pressure inside the eye (greater than 21 millimeters of mercury, or mm Hg) but
without any evidence of damage to the optic nerve or loss of visual field. Some
people who have ocular hypertension may still need treatment if the pressure in the
eye is high enough to pose a risk of damaging the optic nerve over the long
Corneal thickness refers to the thickness of the clear
front surface of the eye (cornea). Cornea thickness, along with pressure inside the eye, helps determine your risk for glaucoma.
Mild glaucoma refers to optic nerve damage with a normal
visual field or minimal loss of side, or peripheral, vision. If signs of optic
nerve damage are present without visual field loss, the person may be
considered as possibly having glaucoma (a glaucoma
Moderate glaucoma refers to optic nerve damage with
moderate loss of vision in at least one eye. But sight in the center of
the eye (central vision) is not affected.
Severe glaucoma refers to optic nerve damage with loss of
vision in both eyes or loss of sight in one eye that includes central vision
The two basic types of glaucoma differ in relation to the cause of
the optic nerve damage. A simple test (gonioscopy) can help your doctor know what type of
glaucoma may be present. Treatment is based on the type of glaucoma.
closed-angle glaucoma, the iris (the colored part of
the eye) and the lens block the movement of fluid between the chambers of the
eye. The blockage causes pressure to
build up and makes the iris press on the drainage system (trabecular meshwork)
of the eye. The increased pressure damages the optic nerve.
open-angle glaucoma, the iris and lens do not block
the movement of fluid between the chambers of the eye. The cause of the optic
nerve damage in open-angle glaucoma is not well understood. It may be that the
fluid does not drain out of the eye normally. It may be that as a person ages,
his or her eyes have more exposure to risk factors or are more likely to be
injured. People may also inherit the tendency to develop glaucoma.
In this article
This information is produced and provided by the National
Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National
Institute via the Internet web site at http://
.gov or call 1-800-4-CANCER.
WebMD Medical Reference from Healthwise
February 28, 2012
This information is not intended to replace the advice of a doctor.
Healthwise disclaims any liability for the decisions you make based on this