What is Glaucoma?

Posted on April 1st, 2009 by admin


What is Glaucoma?
 
Glaucoma is a disease that characterized as permanent loss of vision as a result of damage to the optic nerve in the back of the eye, by an increase pressure of the fluid in the eye.
 

What Causes Glaucoma?
The eye constantly produces aqueous, the clear fluid that fills the anterior chamber (the space between the cornea and iris). The aqueous is being filtered out of the anterior chamber through a complex drainage system. The delicate balance between the production and drainage of aqueous determines the eye’s intraocular pressure (IOP). Most people's IOPs fall between 8 and 21 (mm Hg). However, some eyes can tolerate higher pressures than others. That's why it may be normal for one person to have a higher pressure than another.


Types of Glaucoma

  1. Open Angle
    Open angle (also called chronic open angle or primary open angle) is the most common type of glaucoma. With this type, even though the anterior structures of the eye appear normal, aqueous fluid builds up within the anterior chamber, causing the IOP to become elevated. Left untreated, this may result in permanent damage of the optic nerve and retina. Eye drops are generally prescribed to lower the eye pressure. In some cases, surgery is performed if the IOP cannot be adequately controlled with medical therapy.
     
  2. Acute Angle Closure
    Only about 10% of the population with glaucoma has this type. Acute angle closure occurs because of an abnormality of the structures in the front of the eye. In most of these cases, the space between the iris and cornea is more narrow than normal, leaving a smaller channel for the aqueous to pass through. If the flow of aqueous becomes completely blocked, the IOP rises sharply, causing a sudden angle closure attack.
    While patients with open angle glaucoma don't typically have symptoms, those with angle closure glaucoma may experience severe eye pain accompanied by nausea, blurred vision, rainbows around lights, and a red eye. This problem is an emergency and should be treated by an ophthalmologist immediately. If left untreated, severe and permanent loss of vision will occur in a matter of days.
     
  3. Secondary Glaucoma
    This type occurs as a result of another disease or problem within the eye such as: inflammation, trauma, previous surgery, diabetes, tumor, and certain medications. For this type, both the glaucoma and the underlying problem must be treated.
     
  4. Congenital
    This is a rare type of glaucoma that is generally seen in infants. In most cases, surgery is required.
     

    Diagnosis of Glaucoma

There are four (4) important factors in the diagnosis of glaucoma: intraocular pressure, the condition of the optic nerve, the patient's visual field and the angle where the iris meets the cornea. To detect these factors, the ophthalmologist will do the following diagnostic tests:

  • Tonometry - used to measure
    pressure. Drops are put in the eyes to numb the eye and then the doctor measures the eye pressure, using an instrument called a tonometer. This instrument measures the inner pressure of the eye by determining how much pressure is necessary to cause a slight indentation on the outer part of the eye. 
    • Ophthalmoscopy - used to examine the inside of the eye, the optic nerve and the patient's field of vision. Drops are put in the eyes to dilate the pupil and then the doctor uses an instrument called an ophthalmoscope that lights up and magnifies the inside of the eye.
    If the intraocular pressures are not within normal range or if the optic nerve looks unusual, the doctor may do a perimetry or a gonioscopy:
  • Perimetry - a special test that produces a map of the complete field of vision. 
    • Gonioscopy - a test to check whether the angle where the iris meets the cornea is open or closed.
 

Treatment of Glaucoma

Most patients with glaucoma require only medication to control the eye pressure. Sometimes, several medications that complement each other are necessary to reduce the pressure adequately.

Surgery is indicated when medical treatment fails to lower the pressure satisfactorily. There are several types of procedures, some involve laser and can be done in the office, others must be performed in the operating room. The objective of any glaucoma operation is to allow fluid to drain from the eye more efficiently.
Prevention of Glaucoma

While glaucoma cannot be prevented, the earlier it is diagnosed the better. Recommendations for early detection include:

- Have a test every two to four years if you are between the ages of 40 and 65. 

- Have a test every one to two years if you: 

- Are 65 years of age or older 

- Have a family history of glaucoma 

- Are of Black or Asian ancestry 

- Have diabetes or a chronic inflammatory disease

- Have had previous serious eye injury 

- Are taking steroids

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