Glaucoma, dangerous but can be prevented
Dr. Injil Abu Bakar, General Practitioner, Boston, Massachusetts
Glaucoma is a leading cause of blindness in the United States, especially among older people. But if glaucoma is treated early, loss of sight can often be prevented.
What is glaucoma?
Glaucoma is a disease of the optic nerve, which is the part of the eye that carries the images we see to the brain. The optic nerve is made up of many nerve fibers, similar to an electric cable containing numerous wires. When pressure inside the eye increases, damage to the optic nerve fibers may occur, causing blind spots, which usually go undetected until the optic nerve has a lot of damage. If the entire nerve is ruined, blindness results.
The optic nerve connects the retina -- the light-sensitive layer of tissue at the back of the eye -- to the brain. A healthy optic nerve is necessary for good vision.
There are several different types of glaucoma. For this article, we will address open-angle glaucoma and closed-angle glaucoma.
Open-angle glaucoma, the most common form of glaucoma, affects about three million Americans. Half of them do not even know they have it. There are no symptoms at first -- vision stays normal, and there is no pain. If the glaucoma remains untreated, people may begin to notice that although they see things in front of them clearly, they miss objects to the side and out of the corners of their eyes.
Open-angle glaucoma gets its name because the angle that allows fluid to drain out of the anterior chamber is open. However, for unknown reasons, the fluid passes too slowly through the meshwork drain. As the fluid builds up, the pressure inside the eye increases. Unless the pressure at the front of the eye is controlled, it can damage the optic nerve and cause vision loss.
With early treatment, you can often prevent serious vision loss and blindness.
With closed-angle glaucoma, the fluid at the front of the eye cannot reach the angle and leave the eye because the angle is blocked by part of the iris (the part that makes eyes blue, brown or green). You can imagine this occurring much like a sheet of paper floating near a drain. If the paper suddenly drops over the opening, the flow is quickly blocked.
People with this type of glaucoma experience a sudden increase in pressure. Symptoms may include:
* Blurred vision
* Severe eye pain
* Headaches
* Rainbow-colored halos around lights
* Nausea and vomiting
This is a true eye emergency. If you have any of these symptoms, see your ophthalmologist right away. Sufferers require immediate treatment to improve the flow of fluid. Without treatment, blindness in the eye can occur in as little as one or two days. Usually, prompt laser surgery can clear the blockage and protect sight.
Who is at risk?
Although anyone can get glaucoma, those who are at greater risk include:
* People over the age of 60
* African-Americans over the age of 40
* People with a family history of glaucoma
* People with diabetes
* People who have had eye injuries in the past
How is glaucoma detected?
Having regular eye examinations by your ophthalmologist is the best way to detect glaucoma. A glaucoma screening that checks only the pressure of the eye is not enough to determine if you have glaucoma.
Your eye doctor also will have to do the following tests:
* Visual acuity: This eye chart test measures how well you see at different distances.
* Visual field: This test measures your side (peripheral) vision.
* Pupil dilatation: With your pupil dilated, your eye doctor is able to get a better look at your optic nerve to check for signs of damage. To do this, your eye doctor places drops into the eye to dilate (widen) the pupil. After the examination, your close-up vision may remain blurred for several hours.
* Tonometry: This test measures the pressure in the eye.