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  • Glaucoma
    Glaucoma

Glaucoma

Glaucoma refers to a group of eye conditions that lead to damage to the optic nerve (the nerve that carries visual information from the eye to the brain).In many cases, damage to the optic nerve is due to increased pressure in the eye, also known as intraocular pressure. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of side vision (peripheral vision). If glaucoma is not diagnosed and treated, it can progress to loss of central vision and blindness.

How common is glaucoma?

Worldwide, glaucoma is the leading cause of irreversible blindness. In fact, as many as 6 million individuals are blind in both eyes from this disease. As many as half of the individuals with glaucoma, however, may not know that they have the disease.

What are glaucoma risk factors?

Glaucoma is often called "the sneak thief of sight." This is because, in most cases, the intraocular pressure can build up and destroy sight without causing obvious symptoms. Thus, awareness and early detection of glaucoma are extremely important because this disease can be successfully treated when diagnosed early. The major risk factors for glaucoma include the following:


  • Age over 45 years
  • Family history of glaucoma
  • Diabetes
  • History of elevated intraocular pressure
  • Nearsightedness (high degree of myopia), which is the inability to see distant objects clearly
  • History of injury to the eye
  • Use of cortisone (steroids), either in the eye or systemically (orally or injected)
  • Farsightedness (hyperopia), which is seeing distant objects better than close ones (Farsighted people may have narrow drainage angles, which predispose them to acute [sudden] attacks of angle-closure glaucoma.)

There are four major types of glaucoma:

  • Open-angle (chronic) glaucoma
  • Angle-closure (acute) glaucoma
  • Congenital glaucoma
  • Secondary glaucoma

The front part of the eye is filled with a clear fluid called aqueous humor. This fluid is always being made in the back of the eye. It leaves the eye through channels in the front of the eye in an area called the anterior chamber angle, or simply the angle.


Anything that slows or blocks the flow of this fluid out of the eye will cause pressure to build up in the eye. This pressure is called intraocular pressure (IOP). In most cases of glaucoma, this pressure is high and causes damage to the major nerve in the eye, called the optic nerve.


Open-angle (chronic) glaucoma is the most common type of glaucoma.


  • The cause is unknown. An increase in eye pressure occurs slowly over time. The pressure pushes on the optic nerve and the retina at the back of the eye
  • Open-angle glaucoma tends to run in families. Your risk is higher if you have a parent or grandparent with open-angle glaucoma.

Angle-closure (acute) glaucoma occurs when the exit of the aqueous humor fluid is suddenly blocked. This causes a quick, severe, and painful rise in the pressure within the eye (intraocular pressure).


  • Angle-closure glaucoma is an emergency. This is very different from open-angle glaucoma, which painlessly and slowly damages vision
  • If you have had acute glaucoma in one eye, you are at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment
  • Dilating eye drops and certain medications may trigger an acute glaucoma attack

Congenital glaucoma often runs in families (is hereditary).It is present at birth and results from the abnormal development of the fluid outflow channels in the eye


Secondary glaucoma is caused by:


  • Drugs such as corticosteroids
  • Eye diseases such as uveitis
  • Systemic diseases

Symptoms

OPEN-ANGLE GLAUCOMA
  • Most people have NO symptoms until they begin to lose vision
  • Gradual loss of peripheral (side) vision (also called tunnel vision)

ANGLE-CLOSURE GLAUCOMA
  • Symptoms may come and go at first, or steadily become worse
  • Sudden, severe pain in one eye
  • Decreased or cloudy vision
  • Nausea and vomiting
  • Rainbow-like halos around lights
  • Red eye
  • Eye feels swollen

CONGENITAL GLAUCOMA
  • Symptoms are usually noticed when the child is a few months old
  • Cloudiness of the front of the eye
  • Enlargement of one eye or both eyes
  • Red eye
  • Sensitivity to light
  • Tearing

How is glaucoma diagnosed?

An eye doctor (ophthalmologist) can usually detect those individuals who are at risk for glaucoma before nerve damage occurs. The doctor also can diagnose patients who already have glaucoma by observing their nerve damage or visual field loss. The following tests, all of which are painless, may be part of this evaluation.


  • Tonometry determines the pressure in the eye.Several types of tonometers are available for this test, the most common being the applanation tonometer. After the eye has been numbed with anesthetic eyedrops, the tonometer's sensor is placed against the front surface of the eye. The firmer the tone of the surface of the eye, the higher the pressure reading.
  • Pachymetry is a relatively new test being used for the diagnosis and treatment of glaucoma. Pachymetry determines the thickness of the cornea. After the eye has been numbed with anesthetic eyedrops, the pachymeter tip is touched lightly to the front surface of the eye (cornea). Recent studies have shown that corneal thickness can affect the measurement of intraocular pressure. Thicker corneas may give falsely high eye pressure readings and thinner corneas may give falsely low pressure readings.
  • Gonioscopy is done by numbing the eye with anesthetic drops and placing a special type of contact lens with mirrors inside the eye. The mirrors enable the doctor to view the interior of the eye from different directions. The purpose of this test is to examine the drainage angle and drainage area of the eye. In this procedure, the doctor can determine whether the angle is open or narrow and find any other abnormalities within the angle area, individuals with narrow angles have an increased risk for a sudden closure of the angle, which can cause an acute angle-closure glaucomatous attack. Gonioscopy can also determine if anything, such as abnormal blood vessels, might be blocking the drainage of the aqueous fluid out of the eye.
  • Ophthalmoscopy is an examination in which the doctor uses a handheld device to look directly through the pupil (the opening in the colored iris) into the eye. This procedure is done to examine the optic nerve (seen as the optic disc) at the back of the eye. Damage to the optic nerve, called cupping of the disc, can be detected in this way. Cupping, which is an indentation of the optic disc, can be caused by increased intraocular pressure. Additionally, a pale color of the nerve can suggest damage to the nerve from poor blood flow or increased intraocular pressure. Special cameras can be used to take photographs of the optic nerve to compare changes over time.
  • Visual Field testing actually maps the visual fields to detect any early (or late) signs of glaucomatous damage to the optic nerve. This test can be grossly done by having the patient look straight ahead with one eye covered and count the fingers shown by the examiner from the side. More typically, however, visual fields are measured by a computerized assessment. For this procedure, one eye is covered and the patient places his or her chin in a type of bowl. Then, when the patient sees lights of various intensities and at different locations, he or she pushes a button. This process produces a computerized map of the visual field, outlining the areas where the eye can or cannot see.

Other, more sophisticated tests may also be employed. All of these tests need to be repeated at intervals to assess the progress of the disease and the effect of the treatment.

How often should someone be checked (screened) for glaucoma?

An eye doctor (ophthalmologist) can usually detect those individuals who are at risk for glaucoma before nerve damage occurs. The doctor also can diagnose patients who already have glaucoma by observing their nerve damage or visual field loss. The following tests, all of which are painless, may be part of this evaluation.


  • Age 20-29: Individuals of African descent or with a family history of glaucoma should have an eye examination every three to five years. Others should have an eye exam at least once during this period.
  • Age 30-39: Individuals of African descent or with a family history of glaucoma should have an eye examination every two to four years. Others should have an eye exam at least twice during this period.
  • Age 40-64: Individuals should have an eye examination every two to four years.
  • Age 65 or older: Individuals should have an eye examination every one to two years.

These routine screening eye examinations are mandatory since glaucoma usually causes no symptoms (asymptomatic) in its early stages. Once damage to the optic nerve has occurred, it cannot be reversed. Thus, in order to preserve vision, glaucoma must be diagnosed early and followed regularly. Patients with glaucoma need to be aware that it is a lifelong disease. Compliance with scheduled visits to the eye doctor and with prescribed medication regimens offers the best chance for maintaining vision.

What is the treatment for glaucoma?

General approach

Although nerve damage and visual loss from glaucoma cannot usually be reversed, glaucoma is a disease that can generally be controlled. That is, treatment can make the intraocular pressure normal and, therefore, prevent or retard further nerve damage and visual loss. Treatment may involve the use of eye drops, pills (rarely), laser, or surgery.


Eye drops are usually used first in treating most types of open-angle glaucoma. In contrast, in Europe, laser or surgery is sometimes the first choice of treatment. One or more types of eye drops may have to be taken up to several times a day to lower intraocular pressure. These drops work either by reducing the production of the aqueous fluid (shutting the faucet) or by increasing the drainage of the fluid out of the eye. Each type of therapy has its benefits and potential complications.


Glaucoma medications (eye drops)

These drops work in the treatment of glaucoma by reducing the production of the aqueous humor. For years, they have been the gold standard for treating glaucoma. Newer drops have fewer side effects than those used in the past and also protect the optic nerve from glaucoma damage.


Used once or twice daily, these drops are very effective.Ophthalmologists often prescribe an eyedrop containing more than one class of drug to patients who require more than one type of drug for control of their glaucoma. This simplifies the taking of drops by the patient.


Glaucoma surgery or laser

There are several forms of laser therapy for glaucoma. Laser iridotomy involves making a hole in the colored part of the eye (iris) to allow fluid to drain normally in eyes with narrow or closed angles. Laser trabeculoplasty is a laser procedure performed only in eyes with open angles. Laser trabeculoplasty does not cure glaucoma but is often done instead of increasing the number of different eye drops or when a patient's intraocular pressure is felt to be too high despite the use of multiple eye drops (maximal medical therapy). In some cases, it is used as the initial or primary therapy for open-angle glaucoma. This procedure is a quick, painless, and relatively safe method of lowering the intraocular pressure. With the eye numbed by anesthetic drops, the laser treatment is applied through a mirrored contact lens to the angle of the eye. Microscopic laser burns to


Argon laser trabeculoplasty (ALT) and Selective laser trabeculoplasty (SLT).

ALT is generally not repeated after the second session due to the formation of scar tissue in the angle. SLT is less likely to produce scarring in the angle, so, theoretically, it can be repeated multiple times. However, the likelihood of success with additional treatments when prior attempts have failed is low. Thus, the options for the patient at that time are to increase the use of eyedrops or proceed to surgery.


Laser cyclo-ablation (also known ciliary body destruction, cyclophotocoagulation or cyclocryopexy) is another form of laser treatment generally reserved for patients with severe forms of glaucoma with poor visual potential. This procedure involves applying laser burns or freezing to the part of the eye that makes the aqueous fluid (ciliary body). This therapy destroys the cells that make the fluid, thereby reducing the eye pressure. This type of laser is typically performed after other more traditional therapies have failed


Glaucoma surgery

Trabeculectomy is a delicate microsurgical procedure used to treat glaucoma. In this operation, a small piece of the clogged trabecular meshwork is removed to create an opening and a new drainage pathway is made for the fluid to exit the eye. As part of this new drainage system, a tiny collecting bag is created from conjunctival tissue. (The conjunctiva is the clear covering over the white of the eye.) This bag is called a "filtering bleb" and looks like a cystic raised area that is at the top part of the eye under the upper lid. The new drainage system allows fluid to leave the eye, enter the bag/bleb, and then pass into the capillary blood circulation (thereby lowering the eye pressure). Trabeculectomy is the most commonly performed glaucoma surgery. If successful, it is the most effective means of lowering the eye pressure.


Aqueous shunt devices (glaucoma implants or tubes) are artificial drainage devices used to lower the eye pressure. They are essentially plastic microscopic tubes attached to a plastic reservoir. The reservoir (or plate) is placed beneath the conjunctival tissue. The actual tube (which extends from the reservoir) is placed inside the eye to create a new pathway for fluid to exit the eye. This fluid collects within the reservoir beneath the conjunctiva creating a filtering bleb. This procedure may be performed as an alternative to trabeculectomy in patients with certain types of glaucoma.


Viscocanalostomy is an alternative surgical procedure used to lower eye pressure. It involves removing a piece of the sclera (eye wall) to leave only a thin membrane of tissue through which aqueous fluid can more easily drain. While it is less invasive than trabeculectomy and aqueous shunt surgery, it also tends to be less effective.


The surgeon sometimes creates other types of drainage systems. While glaucoma surgery is often effective, complications, such as infection or bleeding, are possible. Accordingly, surgery is usually reserved for cases that cannot otherwise be controlled.

Depending on the type of glaucoma, the treatment can be summarized as follows:

Open-angle glaucoma treatment:

Most people with open-angle glaucoma can be treated successfully with eye drops. Most eye drops used today. You may need more than one type of drop. Some patients will need other forms of treatment, such as a laser treatment, to help open the fluid outflow channels. This procedure is usually painless. Others may need traditional surgery to open a new outflow channel.


Angle-closure glaucoma treatment:

Acute angle-closure attack is a medical emergency. Blindness will occur in a few days if it is not treated. Drops, pills, and medicine given through a vein (by IV) are used to lower pressure. Some people also need an emergency operation, called an iridotomy. This procedure uses a laser to open a new channel in the iris. The new channel relieves pressure and prevents another attack.


Congenital glaucoma treatment:

This form of glaucoma is almost always treated with surgery to open the outflow channels of the angle. This is done while the patient is asleep and feels no pain (with anesthesia).


Expectations (prognosis)

Open-angle glaucoma:

With good care, most patients with open-angle glaucoma can manage their condition and will not lose vision, but the condition cannot be cured. It's important to carefully follow up with your doctor.


Angle-closure glaucoma:

Rapid diagnosis and treatment of an attack is key to saving your vision. Seek emergency care immediately if you have symptoms of an angle-closure attack.


Congenital glaucoma:

Early diagnosis and treatment is important. If surgery is done early enough, many patients will have no future problems.


Calling your health care provider

Call your health care provider if you have severe eye pain or a sudden loss of vision, especially loss of peripheral vision. Call for an appointment with your health care provider if you have risk factors for glaucoma and have not been screened for the condition.


Can glaucoma be prevented?

Primary open-angle glaucoma cannot be prevented, given our current state of knowledge. However the optic-nerve damage and visual loss resulting from glaucoma can be prevented by earlier diagnosis, effective treatment, and compliance with treatment.


Secondary types of glaucoma can often be prevented by avoidance of trauma to the eye and prompt treatment of eye inflammation and other diseases of the eye or body that may cause secondary forms of glaucoma.


Most cases of visual loss from angle-closure glaucomas can be prevented by the appropriate use of laser iridotomy in eyes at risk for the development of acute or chronic angle-closure glaucoma.

What is in the future for glaucoma?

New eyedrops will continue to become available for the treatment of glaucoma. Some drops will be new classes of agents. Other drops will combine some already existing agents into one bottle to achieve an additive effect and to make it easier and more economical for patients to take their medication.


Many researchers are investigating the therapeutic role of neuroprotection of the optic nerve, especially in patients who seem to be having progressive nerve damage and visual field loss despite relatively normal intraocular pressures. Animal models have shown that certain chemical mediators can reduce injury or death of nerve cells. Proving such a benefit for the human optic nerve, however, is more difficult because, for one thing, biopsy or tissue specimens are not readily available. Nevertheless, if any of these mediators in eyedrops can be shown to protect the human optic nerve from glaucomatous damage, this would be a wonderful advance in preventing blindness.


In other studies, new surgical methods are being evaluated to lower the intraocular pressure more safely without significant risk of damage to the eye or loss of vision.


Finally, increased efforts to enhance public awareness of glaucoma, national free screenings for those individuals at risk, earlier diagnosis and treatment and better compliance with treatment are our best hopes to reduce vision loss from glaucoma.

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