Glaucoma

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What is glaucoma?

Glaucoma is an eye disease in which the nerve that connects the eye to the brain (optic nerve) is damaged. The damage can lead to a loss of vision. However, early treatment can prevent blindness.

How does it occur?

Normally, the fluid in the front of the eye (called the aqueous humor) flows from the ciliary body, where it is formed to the front of the eye. The fluid drains from the angle (where the iris and cornea come together). The tissue that drains fluid from the angle is called the trabecular meshwork. This fluid nourishes your eye and helps to keep its shape. Glaucoma occurs when the aqueous humor drains out of the eye too slowly, causing the pressure in the eye to increase. Higher pressure damages the optic nerve.

In some cases glaucoma develops even though the eye pressure is normal.

There are 2 main types of glaucoma, depending on how the flow of fluid is blocked:

• Open-angle glaucoma is caused by a gradual blockage in the trabecular meshwork. It is the more common type of glaucoma in the US and Europe. It usually affects both eyes.
• Angle-closure glaucoma is a blockage caused by a change in the position of the iris (the colored part of the eye). The change in position causes the iris to block the drainage channels. This type of glaucoma usually happens in one eye at a time. If you get glaucoma in one eye, you are at risk for having the same problem in the other eye. When this type of glaucoma happens suddenly, it is called acute angle-closure glaucoma and is a medical emergency.

Glaucoma tends to run in families. It is a common eye problem in people over age 60. You have an increased risk of open-angle glaucoma if you are African American or a family member has glaucoma. On the other hand, angle-closure glaucoma is more common among Asian people than white people, and it is rare in African Americans.

What are the symptoms?

Open-angle and other chronic forms of glaucoma often have no symptoms in the early stages. In later stages, you will begin to notice a loss of vision. Side vision is affected first.

Symptoms of acute angle-closure glaucoma include:

• severe eye pain
• seeing halos around lights
• nausea and vomiting
• headache
• loss of vision

How is it diagnosed?

Your healthcare provider may screen you for vision problems during your routine checkups. If you have vision problems, your provider will refer you to an eye care provider.

The eye care provider may use the following tests to diagnose glaucoma:

• tonometry, a painless procedure used to measure the pressure in your eyes
• ophthalmoscopy, in which the provider uses an instrument to look at the optic nerve inside your eye
• visual field testing, which can show early changes in your side vision caused by damage to the optic nerve
• gonioscopy, which is a way to examine the drainage channels with a mirrored lens
• pachymetry, which is a painless way to measure the thickness of your cornea

How is it treated?

The goal in the treatment of glaucoma is to reduce the pressure in your eyes and decrease damage to the optic nerve. This may be done with eyedrops, medicine taken by mouth, laser surgery, or other types of surgery. Some eyedrops reduce the amount of fluid made by your eye. Others increase the amount of fluid that flows out. Surgery relieves pressure inside the eye by opening up the drainage channel or by making another opening through which the fluid can drain.

Make sure your healthcare provider tells you about possible side effects of any medication you are taking. If you have concerns, call your provider.

How long will the effects last?

Loss of vision caused by glaucoma is permanent. This is why glaucoma needs to be diagnosed and treated early to stop further damage to the optic nerve.

If your healthcare provider prescribes medication to control the pressure, you may need to take it for the rest of your life.

How can I take care of myself?

• Take your medication as prescribed.
• Carefully follow your healthcare provider's recommendations for follow-up visits and pressure measurements.
• Call your healthcare provider if you have any side effects from your medication.

How can I help prevent glaucoma?

Glaucoma cannot be prevented. However, blindness can be prevented if glaucoma is treated before pressure in the eye has damaged the optic nerve too much.

You may be able to help prevent glaucoma from becoming severe if you:

• Have a regular eye exam. How often you need to see the eye care provider will depend on how severely your optic nerve was damaged.
• At your eye exam, make sure the pressure in your eye is measured and that your optic nerve is examined.
• Learn about your family history. Chronic open-angle glaucoma often runs in families.
• See your healthcare provider at once if you see halos around lights or notice any changes in your vision.

Reviewed for medical accuracy by faculty at the Wilmer Eye Institute at Johns Hopkins. Web site: http://www.hopkinsmedicine.org/wilmer/

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