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What is glaucoma? | Types | Symptoms | Risk factors | Examination for glaucoma | Treatment

What is glaucoma?

Glaucoma is a group of diseases associated with increased pressure in the eye. This pressure is called intraocular pressure or IOP. Although glaucoma can't be prevented, blindness resulting from glaucoma can. Glaucoma is one of the leading causes of preventable blindness in the United States. In fact, it accounts for nine to twelve percent of all cases of blindness, and is the most common cause of blindness among African-Americans. Blacks are five times more likely to get glaucoma than whites. Glaucoma is four times more likely to cause blindness in blacks than in whites. It is fifteen times more likely to cause blindness in blacks between the ages of forty-five and sixty-four than in whites of the same age group.

Two and one-half million Americans over age forty have glaucoma, eighty thousand Americans are blind from it, and one million are at risk for blindness because they don't know they have it. Vision loss from glaucoma can be prevented if caught in time. If a person has a relative with glaucoma, is very nearsighted, or has diabetes, he or she is at high risk for glaucoma.

Glaucoma occurs when increased intraocular pressure damages optic fibers within the optic nerve, causing blind spots to develop.

There is a space in the front of the eye called the anterior chamber . It is filled with a clear fluid that flows in and out of the eye continually to nourish nearby tissues . Normally the fluid leaves the anterior chamber at the angle where the cornea and iris meet. A spongy network located there filters the fluid as it leaves the anterior chamber. If the fluid doesn't drain properly, excessive pressure builds up and can damage the optic nerve.

It isn't necessary to have high intraocular pressure for glaucoma to occur. In fact, only about ten percent of the people with elevated pressure have glaucoma. And, ten to fifty percent of the people with glaucoma have a normal intraocular pressure.

About ninety percent of glaucoma cases are chronic, meaning pressure builds up undetected for years. Acute glaucoma is caused by a sudden increase in eye pressure. This condition is rare and tends to be hereditary. It seems to primarily affect people who are farsighted.

Types

Fluid normally flows through the pupil of the eye into the anterior chamber. It leaves the anterior chamber at the angle where the iris and cornea meet. In open-angle glaucoma, this angle is open, but fluid passes too slowly through the filtration area to the drainage canals. As the fluid builds up, pressure rises and causes optic nerve damage which results in vision loss.

In closed-angle glaucoma, the angle between the cornea and iris becomes blocked by part of the iris. Fluid cannot leave the eye and pressure builds quickly. The patient may experience pain and nausea along with redness of the eye and blurred vision. Patients must receive immediate medical attention to clear the blockage and improve the flow of fluid. Without treatment, blindness can occur in just a day or two.

In normal (or low) tension glaucoma, optic nerve damage occurs although the patient's intraocular pressure is considered within normal limits.

Childhood glaucoma is rare and is thought to be hereditary. It may start in infancy, childhood, or adolescence. There are few symptoms in the early stages. However, if left untreated, blindness results.

Congenital glaucoma appears soon after birth or in the first year. Symptoms include tearing, light sensitivity, and cloudiness of the cornea. More common in boys, congenital glaucoma can affect one or both eyes.

Glaucoma can be primary or secondary. The primary condition can't be attributed to any known cause whereas the secondary condition can be traced to some cause such as a previous injury or illness. Secondary glaucoma usually develops as the result of other medical conditions. They sometimes result from eye surgery, advanced cataracts, eye tumors, or eye inflammations. Corticosteroid drugs can also cause glaucoma.

Pigmentary glaucoma occurs because pigment from the iris breaks off and blocks the drainage areas. Another type, neovascular glaucoma, is associated with diabetes.

Symptoms

Most people don't have any symptoms from glaucoma until they begin to lose their vision. As the optic fibers are damaged, blind spots began to appear in the vision. This usually begins occurring from the side causing the person to lose his or her peripheral vision. Because it happens so slowly, the patient often doesn't notice the vision loss until considerable damage has occurred. Blindness will result if too many nerve cells are destroyed

Other symptoms of glaucoma include the inability to adjust the eye to darkened rooms, difficulty focusing on close work, rainbow colored rings or halos around lights, and the need to change eyeglass prescriptions frequently.

If you are experiencing some of the symptoms described here, it does not necessarily mean you have glaucoma. However, if you experience one or more of these symptoms, you should contact your eye doctor for a complete exam. Click here for information on emergency or immediate care.

Risk factors

The risk of developing glaucoma increases with age. People over age thirty-five are at a higher risk of developing glaucoma. Glaucoma appears to run in families. Anyone who has a close relative with glaucoma should have annual eye exams. People who are extremely nearsighted have a higher risk of developing open angle glaucoma while people who are extremely farsighted have a high risk of developing closed-angle glaucoma. People with diabetes or high blood pressure may develop glaucoma. Certain races are more likely to get glaucoma than others, including people of African ancestry who are at an increased risk for developing open angle glaucoma. People of Chinese, Japanese and Southeast Asian descent have a higher probability of developing closed-angle glaucoma. People with cardiovascular disease or conditions that result in poor blood flow to the eye have an increased risk of developing glaucoma. Finally, obesity has been identified as a possible risk factor. If you have any of these risk factors and notice any changes in your vision, you should contact your doctor immediately.

Examination for glaucoma

To check for glaucoma, the ophthalmologist measures intraocular pressure (IOP) in the eye using a tonometer, which has a pressure-sensitive tip that is placed gently near or against the eye.

Some ophthalmic practices use a test where a brief puff of air is directed onto the eye and the resistance of the eye to the puff of air is measured. This test is extremely uncomfortable for many patients and is not used by The Regional Eye Center.

In some cases, the doctor may use a short-acting anesthetic to numb the eye for this examination. Elevated intraocular pressure is sometimes called ocular hypertension, meaning the intraocular pressure is higher than normal. Although this doesn't necessarily mean you have glaucoma, it does mean you may be at increased risk and should have regular eye exams.

The ophthalmologist may use a gonioscope to inspect the drainage angle. It has a special lens that is used to examine the area between the iris and cornea for blockage. By dilating the eye and looking at the optic nerve with an ophthalmoscope, the doctor can evaluate nerve damage and look for larger than normal "cupping" of the optic nerve. The larger the cup, the greater the risk of glaucoma.

The most up-to-date test for glaucoma utilizes the GDx Nerve Fiber Layer Analyzer. The GDx Nerve Fiber Layer Analyzer allows the detection of glaucoma up to five years earlier than traditional methods. Early detection is a key factor in successfully treating glaucoma and preventing vision loss. If glaucoma is detected early, treatment can begin before damage to the nerve layer occurs.

The GDx Never Fiber Layer Analyzer uses polarized light to measure the thickness of the nerve fiber layer at 65,536 points in the retina. Thinning of the nerve fiber layer is associated with damage from glaucoma. Thinning has also been correlated with vision loss in glaucoma patients. In addition to measuring the thickness of the nerve fiber layer, the GDx analyzes the measurement results and compares them to a database of values for a healthy eye of a person of the same age and race.

The test, which is safe and painless, takes only a few minutes to perform and generally doesn’t require the eye to be dilated. Most insurance companies cover the cost of the test.

The GDx Analyzer not only helps detect the presence of glaucoma before symptoms occur, it allows the physician to monitor the glaucoma patient to ensure that the disease is under control. It will help determine treatment needs to be more or less aggressive. All patients who have glaucoma or who have a history of elevated eye pressure should be tested. In addition, patients with a family history of glaucoma or who take certain medications that put them at a higher risk for glaucoma should also be tested.

Treatment

There is no cure for glaucoma, but it can be controlled. Once a diagnosis of glaucoma is made, treatment will most likely need to continue for the rest of the patient's life. In addition, patients must have regular eye exams to ensure the glaucoma remains under control. Although this may seem like a great deal of trouble, it is preferable to the alternative - blindness.

Treatment focuses on lowering intraocular pressure to a level that the ophthalmologist thinks won't cause further nerve damage. This level is known as the "target pressure." Target pressure may differ from person to person and at different times in a person's life. Glaucoma may be treated using medications and/or surgery.

Medications

Medications may be topical or oral. Topical medications include eye drops, wafer-like strips of medication called inserts you put in the corner of your eye, and eye ointments. Oral medications may be in the form of pills or tablets.

Topical medications control or reduce intraocular pressure in one of two ways. Miotics and epinephrine compounds increase the outflow of liquid from the eye. Beta-blockers, carbonic anhydrase inhibitors, and alpha-adrenergic agonists are designed to reduce the amount of fluid produced in the eye.

Prostaglandin analogs, a new group of drugs, reduce intraocular pressure by working near the drainage area of the eye to increase the secondary route of fluid outflow.

The most common oral medications are carbonic anhydrase inhibitors, which slow production of fluid in the eye.

Generally, glaucoma medications need to be taken several times a day. Taking medications as prescribed is very important. Because glaucoma produces no pain or symptoms, people may forget to take their medication or be tempted to stop it. The result will be damage to their vision.

Possible Side Effects

Although side effects of most glaucoma medications aren't serious and usually disappear, they should be discussed with the doctor. They may include stinging or redness of eyes; blurred vision; headaches; changes in pulse, heartbeat, or breathing; changes in sexual desire; mood changes; tingling of fingers and toes; drowsiness; and loss of appetite. People with light-colored eyes who are taking prostaglandin analogs may experience a change in the color of their iris.

 Surgery

Sometimes surgery is necessary to help control glaucoma. The type of surgery depends on a number of factors including type and severity of glaucoma, other eye problems, and general health conditions.

Laser surgery

Laser surgery is usually done on an outpatient basis. Eye drops are used to numb the eye. There is little discomfort, so eye drops are the only anesthesia needed. Little recuperation is needed although the patient may experience some local eye irritation. Normally the patient can resume normal activities within a day or two.

Trabeculoplasty is most common surgery used to treat open angle glaucoma. The ophthalmic surgeon uses a laser to place "spot welds" in the trabecular meshwork, or drainage area of the eye. This stretches the drainage holes in the meshwork and allows the fluid to drain more freely.

Iridotomy is used to treat closed angle glaucoma. The surgeon makes a small hole in the iris, allowing the fluid to move more freely in the eye.

Cyclophotocoagulation is used to treat advanced or aggressive cases of glaucoma.

A laser beam is used to freeze selected areas of the ciliary body, which is the part of the eye that produces the fluid. This procedure reduces the production of fluid.

Incisional surgery

Incisional surgery may be done if vision loss is rapid or medication and/or laser surgery fail to lower intraocular pressure enough. Filtering surgery is done at an outpatient center or hospital. In addition to receiving a local anesthesia, the patient may be sedated. The surgeon removes a tiny piece of the wall of the eye to form a tiny hole. The fluid can then drain through the hole, reducing intraocular pressure. The bloodstream reabsorbs the fluid. The surgeon may place a tiny tube or valve in the eye through the small hole in the sclera. This valve acts as a regulator. When the pressure reaches a certain level, the valve opens to allow fluid to drain out and reduce the pressure. The recovery period for this type of surgery is short. The patient will need to wear a patch for a few days and avoid activities such as swimming that expose the eye to water. The patient will also need to avoid heavy exercise, straining, or driving.

Possible complications from surgery include infection, bleeding, undesirable changes in intraocular pressure, and loss of vision.