Video: What is Glaucoma?
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This video animation provides basic information about glaucoma, an eye disease that can gradually steal your vision.
Glaucoma is a group of eye diseases that cause damage to the optic nerve. The optic nerve is the part of the eye that carries the images we see to the brain. Glaucoma is often called the silent thief of sight, gradually stealing without warning and often without symptoms. If left untreated, glaucoma can lead to blindness.
It was once thought that elevated pressure inside the eye was the main cause of optic nerve damage. Although elevated pressure is clearly a risk factor, we now know that other factors must also be involved because even people with "normal" pressure can experience vision loss from glaucoma.
How Fluid Circulates in the Eye
To understand how glaucoma develops we must first understand how fluid circulates within the eye. Fluid is produced inside of the eye by a structure known as the ciliary body. This structure is located just beneath the iris. The fluid then travels through the pupil, and exits via the eye's drainage system, called the trabecular meshwork.
In healthy eyes, there is a normal balance between the fluid that is made in the eye and the fluid that leaves the eye. Therefore, this fluid creates a relatively constant and healthy pressure within the eye. This pressure is needed to keep the eye inflated, nourished, and functioning properly. This is what we mean by the "eye pressure," and your eye doctor measures routinely.
Open-angle glaucoma is the most common form of adult glaucoma and can lead to loss of vision or blindness. This type of glaucoma can only be detected by your eye care practitioner through a routine eye examination.
Open-angle glaucoma occurs when the eye's drainage system becomes clogged over time. A part of this system, called the trabecular meshwork, is a tiny spongy tissue that allows fluid to leave the eye. This structure is situated in the eye's angle, where the iris and cornea meet. When this drain becomes clogged, aqueous fluid cannot leave the eye as fast as it is produced, causing the fluid to back up. This backed-up fluid increases pressure in the eye and can cause damage to eyesight.
If open-angle glaucoma is not diagnosed and treated, it can cause a gradual loss of vision. This type of glaucoma develops slowly and usually without symptoms.
A small percentage of people with glaucoma have a condition known as narrow-angle glaucoma. This type of glaucoma can occur slowly and progressively, or very quickly, and can only be detected through a comprehensive eye exam. Narrow-angle glaucoma usually occurs in far-sighted people, because they tend to have anterior chambers that are smaller than normal.
In cases of narrow-angle glaucoma, the iris can bow forward, thinning the angle that normally drains the eye. As the angle becomes smaller, fluid backs up and pressure in the eye, or intraocular pressure, begins to rise. If narrow-angle glaucoma is not diagnosed and treated, it can cause loss of vision.
In some cases, narrow-angle glaucoma can lead to an emergency condition known as angle-closure glaucoma. For more information, ask your doctor about narrow-angle glaucoma.
Last reviewed on August 27, 2012