Glaucoma is a disease that damages the eye’s optic nerve. The optic nerve is connected to the retina — a layer of light-sensitive tissue lining the back of the eye — and is made up of many nerve fibers, like an electric cable is made up of many wires. It is the optic nerve that sends signals from your retina to your brain, where these signals are interpreted as the images you see.

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In the healthy eye, a clear fluid called aqueous (pronounced AY-kwee-us) humor circulates inside the front portion of your eye. To maintain a constant healthy eye pressure, your eye continually produces a small amount of aqueous humor while an equal amount of this fluid flows out of your eye. If you have glaucoma, the aqueous humor does not flow out of the eye properly. Fluid pressure in the eye builds up and, over time, causes damage to the optic nerve fibers.

Glaucoma can cause blindness if it is left untreated. Only about half of the estimated three million Americans who have glaucoma are even aware that they have the condition. When glaucoma develops, usually you don’t have any early symptoms and the disease progresses slowly. In this way, glaucoma can steal your sight very gradually. Fortunately, early detection and treatment (with glaucoma eyedrops, glaucoma surgery or both) can help preserve your vision.

There are several types of glaucoma:

Open-angle glaucoma

The most common form of glaucoma is called primary open-angle glaucoma. It occurs when the trabecular meshwork of the eye gradually becomes less efficient at draining fluid. As this happens, your eye pressure, called intraocular pressure (IOP), rises. Raised eye pressure leads to damage of the optic nerve. Damage to the optic nerve can occur at different eye pressures among different patients. Your ophthalmologist (Eye M.D.) establishes a target eye pressure for you that he or she predicts will protect your optic nerve from further damage. Different patients have different target pressures.

Typically, open-angle glaucoma has no symptoms in its early stages and your vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You usually won’t notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. If all the optic nerve fibers die, blindness results.

Half of patients with glaucoma do not have high eye pressure when first examined. Some such individuals will only occasionally have high eye pressures on repeat testing; thus, a single eye pressure test misses many with glaucoma. In addition to routine eye pressure testing, it is essential that the optic nerve be examined by an ophthalmologist for proper diagnosis.

Normal-tension glaucoma

Eye pressure is expressed in millimeters of mercury (mm Hg), the same unit of measurement used in weather barometers.

Although normal eye pressure is considered a measurement less than 21 mm Hg, this can be misleading. Some people have a type of glaucoma called normal-tension, or low-tension glaucoma. Their eye pressure is consistently below 21 mm Hg, but optic nerve damage and visual field loss still occur. People with normal-tension glaucoma typically receive the same methods of treatment used for open-angle glaucoma.

Conversely, ocular hypertension is a condition where someone has higher eye pressure than normal, but does not have other signs of glaucoma, such as optic nerve damage or blank spots that show up in their peripheral (side) vision when tested. Individuals with ocular hypertension are at higher risk for developing glaucoma later relative to those with lower, or average, eye pressure. Just like people with glaucoma, people with ocular hypertension need to be closely monitored by an ophthalmologist to ensure they receive appropriate treatment.

Closed-angle glaucoma, narrow-angle glaucoma or angle-closure glaucoma

A less common form of glaucoma is closed angle (or narrow-angle glaucoma or angle-closure glaucoma). Closed-angle glaucoma occurs when the drainage angle of the eye becomes blocked. Unlike open-angle glaucoma, eye pressure usually goes up very fast. The pressure rises because the iris — the colored part of the eye — partially or completely blocks off the drainage angle. People of Asian descent and those with hyperopia (farsightedness) tend to be more at risk for developing this form of glaucoma.

If the drainage angle becomes completely blocked, eye pressure rises quickly resulting in a closed-angle glaucoma attack. Symptoms of an attack include:

  • Severe eye or brow pain
  • Redness of the eye
  • Decreased or blurred vision
  • Seeing colored rainbows or halos
  • Headache
  • Nausea
  • Vomiting

A closed-angle glaucoma attack is a medical emergency and must be treated immediately. Unfortunately, people at risk for developing closed-angle glaucoma often have few or no symptoms before the attack.

People at risk for closed-angle glaucoma should avoid over-the-counter decongestants and other medications where the packaging states not to use these products if you have glaucoma.

Congenital glaucoma

Congenital glaucoma is a rare type of glaucoma that develops in infants and young children and can be inherited. While uncommon relative to the other types of glaucoma, this condition can be devastating, often resulting in blindness when not diagnosed and treated early.

Secondary glaucoma

Secondary glaucoma is glaucoma that results from another eye condition or disease. For example, someone who has had an eye injury, someone who is on long-term steroid therapy or someone who has a tumor may develop secondary glaucoma.

CAUSES

A clear fluid called aqueous humor circulates inside the front portion of our eyes. To maintain a constant healthy eye pressure, the eye continually produces a small amount of aqueous humor while an equal amount of this fluid flows out of the eye. The fluid flows out through a very tiny drain called the trabecular meshwork, a complex network of cells and tissue in an area called the drainage angle.

If the drainage angle is blocked, excess fluid cannot flow out of the eye, causing the fluid pressure to increase.
If the drainage angle is blocked, excess fluid cannot flow out of the eye, causing the fluid pressure to increase.

If you have glaucoma, the aqueous humor does not flow through the trabecular meshwork properly. If the drainage angle is become less efficient at draining fluid, as in the common open-angle glaucoma, excess fluid cannot flow out of the eye properly, causing the intraocular pressure (IOP) to increase. Over time, raised IOP causes damage to the nerve fibers. If the drainage angle becomes completely blocked, eye pressure rises quickly, resulting in a narrow-angle glaucoma or angle-closure glaucomaattack, with severe eye and brow pain, nausea and vomiting. This kind of glaucoma attack is a medical emergency and must be treated immediately.

Damage to the optic nerve can occur at different eye pressures among different patients. Your ophthalmologist (Eye M.D.) establishes a target eye pressure for you that he or she predicts will protect your optic nerve from further damage. Different patients have different target pressures.

Some people have a type of glaucoma called normal tension, or low tension glaucoma. Their eye pressure is consistently below 21 mm Hg, but optic nerve damage and visual field loss still occur.

Congenital glaucoma is a rare type of glaucoma that develops in infants and young children. It can be hereditary, and it happens when the eye’s drainage system doesn’t develop fully or correctly before birth.

Glaucoma can often be caused by another eye condition or disease. This is known as secondary glaucoma. For example, someone who has a tumor or people undergoing long-term steroid therapy may develop secondary glaucoma. Other causes of secondary glaucoma include:

  • Eye injury;
  • Inflammation of the eye;
  • Abnormal blood vessel formation from diabetes or retinal blood vessel blockage;
  • Use of steroid-containing medications (pills, eyedrops, sprays); or
  • Pigment dispersion, where tiny fragments or granules from the iris (the colored part of the eye) can circulate in the aqueous humor (the fluid within the front portion of the eye) and block the trabecular meshwork, the tiny drain for the eye’s aqueous humor.

 

If you have received a glaucoma diagnosis from your Eye M.D., your doctor will talk about possibletreatment options, such as glaucoma eyedrops and/or glaucoma surgery.

SYMPTOMS

Symptoms of glaucoma

In its early stages, open-angle glaucoma has no obvious signs. As the disease progresses and more damage occurs, blind spots develop in your peripheral (side) vision. These spots may not be noticeable until the optic nerve has become severely damaged — or until detected by an ophthalmologist during a complete exam.

See a simulation of what vision with glaucoma looks like.

People at risk for closed-angle glaucoma (also called narrow-angle or angle-closure glaucoma), where the eye’s drainage angle becomes blocked, usually have no symptoms before the attack, though some early symptoms can include blurred vision, halos, headache or mild eye pain or redness. At the time of a closed-angle glaucoma attack, symptoms include:

  • Severe eye or brow pain
  • Redness of the eye
  • Decreased or blurred vision
  • Seeing colored rainbows or halos
  • Headache
  • Nausea
  • Vomiting

People with “normal-tension glaucoma” may have eye pressures within normal ranges, but have glaucoma signs and symptoms, such as blind spots in their field of vision and optic nerve damage.

Some people may not have glaucoma symptoms, but may have higher than normal eye pressure (calledocular hypertension). They are considered “glaucoma suspects,” and should be monitored carefully by an ophthalmologist.

Culled from: geteyesmart – http://www.geteyesmart.org/eyesmart/diseases/glaucoma/symptoms.cfm

Image: http://abileneadvancedeyecare.com/eye-insights/glaucoma.html

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