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Alternative namesSecondary glaucoma; Open angle glaucoma; Chronic glaucoma; Closed angle glaucoma; Congenital glaucoma; Acute glaucoma
DefinitionGlaucoma involves increased fluid pressure inside the eye ( intraocular pressure ), which damages the optic nerve and causes partial vision loss and can progress to blindness .
Causes, incidence, and risk factors
Glaucoma is the third most common cause of blindness in the US. There are four major types of glaucoma:
All four types of glaucoma are characterized by increased pressure within the eyeball, and therefore all can cause progressive damage to the optic nerve.
Increased pressure occurs when the fluid within the eye (called aqueous humor) does not drain properly. The pressure pushes on the junction of the optic nerve and the retina at the back of the eye. This reduces the blood supply to the optic nerve, which carries visual information from the eye to the brain.
This loss of blood supply causes the individual nerve cells to progressively die. As the optic nerve deteriorates, blind spots develop in the field of vision. Peripheral (side) vision is affected first, followed by or central (front) vision. Without treatment, glaucoma can eventually cause blindness.
Closed angle (acute) glaucoma may occur in people who were born with a narrow angle between the iris and the cornea (the anterior chamber angle). This is more common in people who are farsighted (they see objects in the distance better than those which are close up). The iris may slip forward and suddenly close off the exit of aqueous humor, and a sudden increase in pressure within the eye follows.
Symptoms of pain, redness, nausea, and visuon loss develop rapidly. Angle closure may be provoked in susceptible persons by the use of drops that dilate the eyes. Attacks may also develop without any obvious triggering event. This is more common in the evening because the eye's pupils naturally dilate in dim light.
Open angle (chronic) glaucoma is by far the most common type of glaucoma. In open angle glaucoma, the iris does not block the drainage angle as it does in acute glaucoma. Instead, the fluid outlet channels within the wall of the eye gradually narrow with time. The disease usually affects both eyes, and over a period of years the consistently elevated pressure slowly damages the optic nerve.
Chronic glaucoma has no early warning signs, and the associated loss of peripheral vision occurs so gradually that it may go unnoticed until a substantial amount of damage and vision loss have occurred. The only way to diagnose glaucoma early is through routine eye examinations.
Secondary glaucoma is caused by other diseases, including eye diseases such as uveitis , systemic diseases, and drugs such as corticosteroids.
Congenital glaucoma, which is present at birth, is the result of defective development of the fluid outflow channels of the eye. Surgery is required for correction. Congenital glaucoma is often hereditary.
Risk factors depend on the type of glaucoma. For chronic glaucoma, risk factors include the following:
People with a family history of open angle glaucoma have twice the risk of developing open angle glaucoma as those who do not. African-Americans have four times the risk of developing open angle glaucoma compared to Caucasian Americans. It is estimated that 1% to 2% of people over 40 have chronic glaucoma, with about 25% of cases undetected.
The risk factors for acute glaucoma include the following:
Acute, congenital, and secondary glaucoma are much less common than chronic glaucoma.
Note: Most people with chronic glaucoma have no symptoms until peripheral visual loss is severe
Signs and tests
A physical examination of the eye may be used to diagnose glaucoma, but because intraocular pressure fluctuates, an examination at a low point would not reveal the condition. Examination of the junction of the optic nerve and the retina with an instrument called an ophthalmoscope is necessary.
A standard ophthalmic examination may include:
The objective of treatment is to reduce the intraocular pressure . Depending on the type of glaucoma, this is achieved by medications or by surgery.
Acute glaucoma is a medical emergency requiring immediate treatment by an emergency center or an ophthalmologist. Intraocular pressure can usually be lowered by medications that may be given orally, intravenously, or topically (as eye drops). Beta-adrenergic blocking agents in the form of eye drops are effective for treatment of open angle glaucoma. Timolol, Betagan and OptiPranolol are examples of some of the drops available. Epinephrine drops are sometimes used in combination with other medications.
In 1996, a drug called Xalatan (latanoprost) was approved by the US Food and Drug Administration (FDA) for the treatment of glaucoma. This topical medication helps drain the aqueous outflow from the eye and lower the intraocular pressure. There are also oral medications that may be given, including Daranide, Diamox, and Neptazane. Oral medication or topical drops may be prescribed separately, or a combination of both may be used.
An emergency operation, called an iridotomy, may be required for the treatment of acute glaucoma. This creates a drainage hole in the iris to relieve the pressure that has build up. This technique can be performed by laser surgery without making an incision in the eye.
People at high risk for closed angle glaucoma may opt to undergo iridotomy before having an attack. Patients who have had an acute episode in the past may undergo the procedure to prevent recurrence.
Laser treatment of the fluid drainage area in the eye may be used to treat open angle glaucoma. In severe cases that are not responsive to medical treatment, surgery can be done to create new outflow channels.
Congenital glaucoma is most often treated with surgery..
Untreated acute glaucoma results in severe and permanent vision loss after the onset of symptoms. Vision can be preserved with prompt treatment.
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 lateral (away from the middle) vision.
There is no prevention for the development of open angle glaucoma. If detected early, further vision loss and blindness may be prevented with treatment. Patients with risk factors for closed angle glaucoma should be evaluated and those at high risk should have laser iridotomy, which will prevent acute attacks.
Careful use of dilating eye drops and systemic anticholinergic medications will minimize the risk of acute attacks in high-risk individuals.
Anyone older than 35 should have tonometry (a check of intraocular pressure ) and ophthalmoscopy examinations every 2 years. More frequent examination is recommended for people who have a family history of glaucoma or other risk factors and/or are African-American.
Update Date: 11/5/2002Raymond S. Douglas M.D., Ph.D. Department of Ophthalmology, UCLA Medical Center, Los Angeles, CA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT