Glaucoma Causes and Symptoms

Glaucoma Causes and Symptoms

The causes of Glaucoma are not fully understood. The following paragraph is a condensed explanation of what is known, but other factors likely play a role as well.

A clear fluid called the aqueous humor circulates inside the eye—it is not part of the tears on the outer surface of the eye. A small amount of aqueous humor is produced constantly, and an equal amount flows out of the eye through a microscopic drainage system. You can think of the flow of aqueous humor as a sink with the faucet turned on all the time. If the drainpipe gets clogged, water collects in the sink and the sink will overflow. Because the eye is a closed structure, the excess fluid cannot overflow if the drain is clogged. So if the drainage system of the eye is blocked, the fluid pressure within the inner eye may increase, which can damage the optic nerve.

There are two types of glaucoma:

Open-Angle Glaucoma

This is the most common type of glaucoma in the United States. Open-angle glaucoma occurs as a result of aging. The drainage angle of the eye becomes less efficient with time, and pressure within the eye gradually increases. If this increased pressure results in optic nerve damage, it is known as chronic open-angle glaucoma. Over 90% of adult glaucoma patients have this type of glaucoma.

Glaucoma Open Angle Overview

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Chronic open-angle glaucoma damages vision so gradually and painlessly that you may not be aware of trouble. Initially, blind spots may develop, but these can go unnoticed until the optic nerve is already badly damaged.

Angle-Closure Glaucoma

Sometimes the drainage angle of the eye may become completely blocked. It’s as though a sheet of paper floating near a drain suddenly drops over the opening and blocks the flow out of the sink. In the eye, the iris (the part that makes your eyes blue or brown) may act like the sheet of paper closing off the drainage angle. When eye pressure builds up suddenly, it is called acute angle-closure glaucoma.

Angle-Closure Glaucoma Overview

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Glaucoma Symptoms

If you have any of these symptoms, call your eye care specialist immediately:

  • Blurred vision
  • Severe eye pain
  • Headache
  • Rainbow halos around lights
  • Nausea and vomiting

Unless a doctor treats acute angle-closure glaucoma quickly, blindness can result. In some patients, the disease has the features of both chronic open-angle glaucoma acute angle-closure glaucoma. This may be called “chronic angle closure glaucoma” or “mixed mechanism glaucoma.”

Who is at risk for glaucoma?

High pressure within the inner eye does not necessarily mean that you have glaucoma. Your glaucoma specialist will put together many different pieces of information to determine your risk for developing the disease. The most important risk factors include:

  • Age
  • Family history of glaucoma
  • Past injuries to the eyes
  • African ancestry

Your eye care specialist will weigh all of these factors before deciding whether you need treatment for glaucoma, or whether you should be monitored closely as a glaucoma suspect. This means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect early signs of damage to the optic nerve.

Glaucoma testing

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How is glaucoma detected?

Regular eye examinations are the best way to detect and treat glaucoma. During a complete and painless examination, your eye doctor will:

  • Measure your intraocular pressure (tonometry)
  • Evaluate any optic nerve damage (ophthalmoscopy)

If necessary, your eye doctor may do additional testing including:

  • Inspect the drainage angle of your eye (gonioscopy)
  • Test the visual field of each eye (perimetry)

Some of these tests may not be necessary for every person. If you have glaucoma, you will need to repeat these tests on a regular basis to determine if glaucoma increasing over time.

Glaucoma Prevention

Regular yearly eye exams may help prevent unnecessary vision loss to glaucoma. Treatment for glaucoma requires teamwork between you and your eye doctor. Your glaucoma specialist can prescribe treatment for the disease, but only you can make sure you take your glaucoma eye drops. Never stop taking or change your glaucoma medications without first consulting with your eye doctor. Frequent eye examinations and tests are critical to monitor your eyes for any changes. Remember, it is your vision, and you must do your part to maintain it!

Glaucoma Treatment


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Visit the American Academy of Opthalmology’s webpage on Glaucoma.