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What is Glaucoma?

what is glaucoma

Glaucoma is an eye disease that usually has no symptoms in its early stages. Without proper treatment, glaucoma can lead to blindness. The good news is that with regular eye exams, early detection, and treatment, you can preserve your sight.

If you have been diagnosed with glaucoma, or are a glaucoma suspect, you probably have a lot of questions and some concerns. Coping with a long-term eye condition can seem overwhelming, but you are fortunate compared to the many who have glaucoma and don’t know it. You are now empowered to learn how you can preserve your vision and live a normal life as a glaucoma patient.

To understand glaucoma, it is important to have an idea of how the eye works and the different parts of the eye.

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Covering most of the outside of the eye is a tough white layer called the sclera. A clear thin layer called the conjunctiva covers the sclera. At the very front of the eye is a clear surface, like a window, called the cornea that protects the pupil and the iris behind that window.

The iris, a muscle, is the colored part of the eye that contracts and expands to let light into the eye. At the center of the iris is a hole (covered by the clear cornea) called the pupil, where light enters the eye.

The lens inside our eye focuses this light onto the back of the eye, which is called the retina. The retina converts the light images into electrical signals, and the retina’s nerve cells and fibers carry these signals to the brain through the optic nerve. The optic disc is the area on the retina where all the nerve fibers come together to become the optic nerve as it leaves the eye to connect to the brain.

Healthy Eye Drainage

The front part of the eye is filled with a clear fluid (called aqueous humor) made by the ciliary body. The fluid flows out through the pupil. It then reaches the eye’s drainage system, including the trabecular meshwork and a network of canals.

The inner pressure of the eye (intraocular pressure or “IOP”) depends on the balance between how much fluid is made and how much drains out of the eye. If your eye’s fluid system is working properly, then the right amount of fluid will be produced. Likewise, if your eye’s drainage system is working properly, then fluid can drain freely out to prevent pressure buildup. Proper drainage helps keep eye pressure at a normal level and is an active, continuous process that is needed for the health of the eye.

The Optic Disc

You have millions of nerve fibers that run from your retina to form the optic nerve. These fibers meet at the optic disc. In most types of glaucoma, the eye’s drainage system becomes clogged so the intraocular fluid cannot drain. As the fluid builds up, it causes pressure to build inside the eye, which can damage these sensitive nerve fibers and result in vision loss. As the fibers are damaged and lost, the optic disc begins to hollow and develops a cupped shape. Doctors can identify this cupping shape in their examinations.

development of glaucoma 2023 update

Intraocular Pressure

A normal intraocular pressure (IOP) ranges between 12 and 22 mmHg (“millimeters of mercury,” a measurement of pressure.) If the pressure remains too high for too long, the extra pressure on the sensitive optic disc can lead to permanent vision loss.

Although high IOP is clearly a risk factor for glaucoma, we know that other factors also are involved because people with IOP in the normal range can experience vision loss from glaucoma. 

Vision Loss in Glaucoma

Glaucoma usually occurs in both eyes, but increased eye pressure tends to happen in one eye first. This damage may cause gradual visual changes and loss of sight over many years. Often, peripheral (side) vision is affected first, so the change in your vision may be small enough that you may not notice it. With time, your central vision may also be affected. Sight lost from glaucoma cannot be restored. However, early detection and treatment can prevent vision loss and maintain remaining vision.

Glaucoma affects people of all ages, from babies to teens to younger and older adults.

Although everyone is at risk for glaucoma, those at higher risk include people who:

  • Are over 60 years old
  • Are of African, Asian, or Hispanic descent
  • Have relatives with glaucoma
  • Are very nearsighted (myopic) or far-sighted (hyperopic)
  • Use steroid medications
  • Have high eye pressure
  • Have a thin central cornea
  • Have had an eye injury

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In the most common form of glaucoma, Primary Open-Angle Glaucoma, buildup of fluid pressure happens very slowly. There are no uncomfortable or painful symptoms. Usually, the initial loss of vision is of side (peripheral) vision, and central vision is maintained until late in the disease. Since we use our central vision for driving, reading and most tasks, the gradual loss of peripheral vision in glaucoma isn’t typically noticed until a significant amount of vision has been permanently lost.

In the less common kinds of glaucoma, symptoms can be noticeable.

These symptoms can include:

Hazy vision

Eye and head pain

Nausea or vomiting

You should see your doctor if you experience any of the symptoms listed above.

Early detection, through regular and complete eye exams, is the key to protecting your vision from damage caused by glaucoma. It is important to have your eyes examined regularly.

You should get a baseline eye screening at age 40. Early signs of eye disease and changes in vision may start to occur at this age. Your eye doctor will tell you how often to have follow-up exams based on the results of this screening. If you have diabetes, high blood pressure, or a family history of glaucoma, you should see an eye doctor now to determine how often to have eye exams.

Learn More

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Glaucoma is a very misunderstood disease. Often, people don’t realize the severity or who is affected.

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After cataracts, glaucoma is the leading cause of blindness in African Americans.

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Everyone is at risk for glaucoma. However, certain groups are at higher risk than others.

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Most people who have open-angle glaucoma don’t notice changes in their vision at first, because it develops slowly.