Definition: Defining the Meaning of Glaucoma
Glaucoma is a term describing a group of ocular (eye) disorders that result in optic nerve damage, often associated with increased fluid pressure in the eye (intraocular pressure)(IOP). The disorders can be roughly divided into two main categories, "open-angle" and "closed-angle" (or "angle closure") glaucoma. Glaucoma tends to be inherited and may not show up until later in life.
Glaucoma is a family of diseases that can damage the eye's optic nerve and result in vision loss and in most extreme cases, blindness. Glaucoma occurs when the normal fluid pressure inside the eyes slowly begins to rise. However, with early diagnosis, you can often treat your eyes and guard them from serious vision loss.
What is the optic nerve
The optic nerve is a bundle of more than 1 million nerve endings. It connects the retina to the brain. The retina is the light-sensitive tissue at the back of the eye. A healthy optic nerve is necessary for good vision.
What are some other forms of glaucoma
Open-angle glaucoma is the most common form. Some people have other types of the disease.
Low-tension or normal-tension glaucoma.
Optic nerve damage and narrowed side vision occur in people with normal eye pressure. Lowering eye pressure at least 30 percent through medicines slows the disease in some people. Glaucoma may worsen in others despite low pressures.
A comprehensive medical history is important in identifying other potential risk factors, such as low blood pressure, that contribute to low-tension glaucoma. If no risk factors are identified, the treatment options for low-tension glaucoma are the same as for open-angle glaucoma.
The fluid at the front of the eye cannot reach the angle and leave the eye. The angle gets blocked by part of the iris. People with this type of glaucoma have a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. If you have these symptoms, you need to seek treatment immediately.
This is a medical emergency. If your doctor is unavailable, go to the nearest hospital or clinic. Without treatment to improve the flow of fluid, the eye can become blind in as few as one or two days. Usually, prompt laser surgery and medicines can clear the blockage and protect sight.
Children are born with a defect in the angle of the eye that slows the normal drainage of fluid. These children usually have obvious symptoms, such as cloudy eyes, sensitivity to light, and excessive tearing. Conventional surgery typically is the suggested treatment, because medicines may have unknown effects in infants and be difficult to administer. Surgery is safe and effective. If surgery is done promptly, these children usually have an excellent chance of having good vision.
These can develop as complications of other medical conditions. These types of glaucomas are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, or uveitis (eye inflammation). Pigmentary glaucoma occurs when pigment from the iris flakes off and blocks the mesh-work, slowing fluid drainage.
Glaucoma is detected through a comprehensive dilated eye exam that includes the following:
- Visual acuity test - This eye chart test measures how well you see at various distances.
- Visual field test - This test measures your peripheral (side vision). It helps your eye care professional tell if you have lost peripheral vision, a sign of glaucoma.
- Dilated eye exam - In this exam, drops are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.
- Pachymetry - The measurement of the thickness of your cornea. Your eye care professional applies a numbing drop to your eye and uses an ultrasonic wave instrument to measure the thickness of your cornea.
- Tonometry - The measurement of pressure inside the eye by using an instrument called a tonometer. Numbing drops may be applied to your eye for this test. A tonometer measures pressure inside the eye to detect glaucoma.
A severe form, called neovascular glaucoma, is linked to diabetes.
Corticosteroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in some people. Treatments include, but are not limited to, medicines, laser surgery, or conventional surgery.
- After cataracts, glaucoma is the leading cause of blindness among African Americans.
- Estimates put the total number of suspected cases of glaucoma at over 60 million worldwide.
- Blindness from glaucoma is 6 to 8 times more common in African Americans than Caucasians.
- African Americans are 15 times more likely to be visually impaired from glaucoma than Caucasians.
- It is estimated that over 2.2 million Americans have glaucoma but only half of those know they have it.
- In the U.S., more than 120,000 are blind from glaucoma, accounting for 9% to 12% of all cases of blindness.
- Glaucoma is the second leading cause of blindness in the world, according to the World Health Organization.
- The most common form, open-angle glaucoma, accounts for 19% of all blindness among African Americans compared to 6% in Caucasians.
- Other high-risk groups include: people over 60, family members of those already diagnosed, diabetics, and people who are severely nearsighted.
Statistics: Glaucoma Type
- Glaucoma causes irreversible blindness and many (50%) of the affected people are unaware of their condition.
- Glaucoma is second only to cataract as the leading cause of preventable blindness in the world. It is estimated that over 65 million people throughout the world are affected by glaucoma.
Open-angle glaucoma accounts for 90% of glaucoma cases in the United States. It is painless and does not have acute attacks. The only signs are gradually progressive visual field loss, and optic nerve changes (increased cup-to-disc ratio on fundoscopic examination).
Closed-angle glaucoma accounts for less than 10% of glaucoma cases in the United States, but as many as half of glaucoma cases in other nations (particularly Asian countries). About 10% of patients with closed angles present with acute angle closure crises characterized by sudden ocular pain, seeing halos around lights, red eye, very high intraocular pressure (>30 mmHg), nausea and vomiting, suddenly decreased vision, and a fixed, mid-dilated pupil. It is also associated with an oval pupil in some cases. Acute angle closure is an emergency.