WHAT IS GLAUCOMA?
Glaucoma is high pressure inside your eye (intraocular pressure)  resulting in optic nerve damage, which may cause loss of vision, usually but not always cause this damage. Glaucoma is a degenerative disease that if left untreated can cause permanent damage to the optic nerve resulting in gradual vision loss and eventual blindness. Damage to the optic nerve is usually caused by an elevated intraocular pressure (IOP). Over time, as the optic nerve fibers are destroyed, peripheral (side) vision is lost.
Glaucoma is a condition in which the normal fluid pressure inside the eyes (intraocular pressure, or IOP) slowly rises as a result of the fluid aqueous humor – which normally flows in and out of the eye – not being able to drain properly. Instead, the fluid collects and causes pressure damage to the optic nerve and loss of vision.
Glaucoma is one of the leading causes of blindness worldwide. Glaucoma can damage your vision so gradually you may not notice any loss of vision until the disease is at an advanced stage. The most common type of glaucoma, primary open-angle glaucoma, has no noticeable signs or symptoms except gradual vision loss.
Early diagnosis and treatment can minimize or prevent optic nerve damage and limit glaucoma-related vision loss. It's important to get your eyes examined regularly, and make sure your eye doctor measures your intraocular pressure. 
TYPES OF GLAUCOMA
  • Open-angle glaucoma
    With this most common type of glaucoma, the fluid that normally flows through the pupil into the anterior chamber of the eye cannot get through the filtration area to the drainage canals, causing a build-up of pressure in the eye. Nearly 3 million Americans – half of whom do not know they have the disease – are affected by glaucoma each year.
  • Low-tension or normal-tension glaucoma
    While normal intraocular pressure ranges between 12 to 21 mm Hg, an individual may have glaucoma even if the pressure is within this range. This type of glaucoma presents optic nerve damage and narrowed side vision.
  • Angle-closure glaucoma
    In angle-closure glaucoma, the fluid at the front of the eye cannot reach the angle and leave the eye, because the angle becomes blocked by part of the iris. This results in a sudden increase in pressure and is generally a medical emergency, requiring immediate treatment to improve the flow of fluid.
  • Childhood glaucoma
    Childhood glaucoma is a rare form of glaucoma that often develops in infancy, early childhood, or adolescence. Prompt medical treatment is important in preventing blindness.
  • Congenital glaucoma
    Congenital glaucoma, a type of childhood glaucoma, occurs in children born with defects in the angle of the eye that slow the normal drainage of fluid. Prompt medical treatment is important in preventing blindness.
  • Primary glaucoma
    Both open-angle and angle-closure glaucoma can be classified as primary or secondary. Primary glaucoma cannot be contributed to any known cause or risk factor.
  • Secondary glaucoma
    Both open-angle and angle-closure glaucoma can be classified as primary or secondary. Secondary glaucoma develops as a complication of another medical condition or injury. In rare cases, secondary glaucoma is a complication following another type of eye surgery.
SYMPTOMS

SYMPTOMS OF GLAUCOMA
The most common types of glaucoma — primary open-angle glaucoma and angle-closure glaucoma — have completely different symptoms.
Primary open-angle glaucoma signs and symptoms include:
  • Gradual loss of peripheral vision, usually in both eyes
  • Tunnel vision in the advanced stages
Acute angle-closure glaucoma signs and symptoms include:
  • Eye pain
  • Nausea and vomiting (accompanying the severe eye pain)
  • Sudden onset of visual disturbance, often in low light
  • Blurred vision
  • Halos around lights
  • Reddening of the eye
Both open-angle and angle-closure glaucoma can be primary or secondary conditions. They're called primary when the cause is unknown and secondary when the condition can be traced to a known cause, such as eye injury, medications, certain eye conditions, inflammation, tumor, advanced cataract or diabetes. In secondary glaucoma, the signs and symptoms can include those of the primary condition as well as typical glaucoma symptoms.

When to see a doctor

Don't wait for noticeable eye problems. Primary open-angle glaucoma gives few warning signs until permanent damage has already occurred. Regular eye exams are the key to detecting glaucoma early enough to successfully treat your condition and prevent further progression of your condition.
The American Academy of Ophthalmology recommends a comprehensive eye exam for all adults starting at age 40, and every three to five years after that if you don't have any glaucoma risk factors. If you have other risk factors or you're older than age 60, you should be screened every one to two years. If you're African-American, your doctor likely will recommend periodic eye exams starting between ages 20 and 39.
In addition, be aware that a severe headache or pain in your eye, nausea, blurred vision, or halos around lights may be the symptoms of an acute angle-closure glaucoma attack. If you experience some or several of these symptoms together, seek immediate care at an emergency room or at an eye doctor's (ophthalmologist's) office right away.
CAUSES
For reasons that doctors don't fully understand, increased pressure within the eye (intraocular pressure) is usually, but not always, associated with the optic nerve damage that characterizes glaucoma. This pressure is due to a buildup of a fluid (aqueous humor) that flows in and out of your eye.
This fluid normally exits your eye through a drainage system at the angle where the iris and the cornea meet. When the drainage system doesn't work properly, the fluid can't filter out of the eye at its normal rate, and pressure builds within your eye.

Primary open-angle glaucoma

In primary open-angle glaucoma, the drainage angle formed by the cornea and the iris remains open, but the drainage channels (trabecular meshwork) in the angle are partially blocked, causing the fluid to drain out of the eye too slowly. This causes fluid to back up in your eye, and pressure gradually increases within your eye.
Damage to the optic nerve doesn't cause symptoms or pain, and it happens so slowly that you may lose an extensive amount of vision before you're even aware of a problem. The exact cause of primary open-angle glaucoma remains unknown.

Angle-closure glaucoma

Angle-closure glaucoma, also called closed-angle glaucoma, occurs when the iris bulges forward to narrow or block the drainage angle formed by the cornea and the iris. As a result, fluid can't adequately flow through and exit your eye, and your eye pressure may increase abruptly. Angle-closure glaucoma usually occurs suddenly (acute angle-closure glaucoma), but it can also occur gradually (chronic angle-closure glaucoma).
Some people with an abnormally narrow drainage angle may be at risk of developing angle-closure glaucoma.
If you have a narrow drainage angle, sudden dilation of your pupils may trigger acute angle-closure glaucoma.

Normal-tension glaucoma

In normal-tension glaucoma, your optic nerve becomes damaged. However, your eye pressure remains within the normal range. Doctors don't understand why this occurs. You may have a sensitive optic nerve, or you may have less blood being supplied to your optic nerve. This lack of blood supply could be caused by atherosclerosis — an accumulation of fatty deposits (plaques) in the arteries — or another condition limiting your blood circulation.

Developmental glaucoma

Some infants or children may be diagnosed with glaucoma. Rarely, some children may be born with glaucoma (congenital glaucoma), develop glaucoma in the first few years of life (infantile glaucoma) or develop glaucoma after age 4 or 5 (juvenile glaucoma). Children usually won't have any symptoms. However, they have optic nerve damage, which may be caused by angle blockages or malformations (primary infantile glaucoma), or it could develop as the result of other conditions (secondary glaucoma).

Pigmentary glaucoma

In pigmentary glaucoma, pigment granules from your iris build up in the drainage channels (trabecular meshwork), slowing or blocking fluid exiting your eye. Physical activities, such as jogging, sometimes stir up the pigment granules, depositing them on the trabecular meshwork and causing intermittent pressure elevations.
RISK FACTOR
Because chronic forms of glaucoma can destroy vision before any signs or symptoms are apparent, be aware of these factors:
  • Elevated internal eye pressure (intraocular pressure). If your internal eye pressure (intraocular pressure) is higher than normal, you're at increased risk of developing glaucoma, though not everyone with elevated intraocular pressure develops the disease.
  • Age. You're at a higher risk of glaucoma if you're older than age 60, particularly if you're Mexican-American. You may be at higher risk of angle-closure glaucoma if you're older than age 40. For certain groups such as African-Americans, however, the risk of developing glaucoma is much higher and occurs at a younger age than that of other groups. If you're African-American, ask your doctor when you should start having regular comprehensive eye exams.
  • Ethnic background. African-Americans older than age 40 have much higher risk of developing glaucoma than do whites (Caucasians). African-Americans also are more likely to experience permanent blindness as a result of glaucoma. People of Asian descent have an increased risk of developing acute angle-closure glaucoma. People of Japanese descent may be more likely to have normal-tension glaucoma.
  • Family history of glaucoma. If you have a family history of glaucoma, you have a greater risk of developing it. Glaucoma may have a genetic link, meaning there's a defect in one or more genes that may cause certain individuals to be more susceptible to the disease. A form of juvenile open-angle glaucoma has been clearly linked to genetic abnormalities.
  • Medical conditions. Several conditions may increase your risk of developing glaucoma, including diabetes, heart diseases, high blood pressure and hypothyroidism.
  • Other eye conditions. Severe eye injuries can cause increased eye pressure. Other eye conditions that could cause increased risk of glaucoma include eye tumors, retinal detachment, eye inflammation and lens dislocation. Certain types of eye surgery also may trigger glaucoma. Also, being nearsighted or farsighted may increase your risk of developing glaucoma.
  • Long-term corticosteroid use. Using corticosteroid medications, especially eyedrops for a long period of time may increase your risk of developing secondary glaucoma.
 COMPLICATIONS
If left untreated, glaucoma will cause progressive vision loss, normally in these stages:
  • Blind spots in your peripheral vision
  • Tunnel vision
  • Total blindness
DIAGNOSIS
  • Visual acuity test – the common eye chart test (see above), which measures vision ability at various distances.
  • Pupil dilation – the pupil is widened with eye drops to allow a close-up examination of the eye's retina.
  • Visual field – a test to measure a person's side (peripheral) vision. Lost peripheral vision may be an indication of glaucoma.
  • Tonometry – a standard test to determine the fluid pressure inside the eye. 

    TREATMENT
    Specific treatment for glaucoma will be determined by your physician based on:
  • Your age, overall health, and medical history
  • Extent of the disease
  • Your tolerance for specific medications, procedures, or therapies
  • Expectations for the course of the disease
  • Your opinion or preference
While glaucoma cannot be cured, early treatment can often control it. Treatment may include:
  • Medications
    Some medications cause the eye to produce less fluid while others lower pressure by helping fluid drain from the eye.
  • Conventional surgery
    The purpose of convention surgery is to create a new opening for fluid to leave the eye.
  • Laser surgery (also called laser trabeculoplasty)
    Several types of surgical procedures can be performed with a laser that are used to treat glaucoma, including:
    • Trabeculoplasty
      In this, most common type of laser surgery to treat open-angle glaucoma, a laser is used to place "spot welds" in the drainage area of the eye (known as the trabecular meshwork) which allows fluid to drain more freely.
    • Iridotomy
      In this procedure, the surgeon uses the laser to make a small hole in the iris – the colored part of the eye - to allow fluid to flow more freely in the eye.
    • Cyclophotocoagulation
      A procedure that uses a laser beam to freeze selected areas of the ciliary body – the part of the eye that produces aqueous humor – to reduce the production of fluid.
  • Tube shunt
    This implantable drainage device creates an artificial pathway in the eye. It is made from a miniature, stainless steel tube, and can be implanted in less than five minutes. A tube shunt is usually selected after it is determined that a patient cannot benefit from conventional surgical treatments.
In some cases, a single surgical procedure is not effective in halting the progress the glaucoma, and repeat surgery and/or continued treatment with medications may be necessary.

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