Secondary glaucoma; Open angle glaucoma; Chronic glaucoma; Closed angle glaucoma; Congenital glaucoma; Acute glaucoma
Glaucoma 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:
- Closed angle (acute) glaucoma
- Open angle (chronic) glaucoma
- Congenital glaucoma
- Secondary 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:
- Age over 40
- Family history of glaucoma
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:
- Older age
- Family history of acute glaucoma
- Use of systemic anticholinergic medications (such as atropine or eye dilation drops) in a high-risk individual
Acute, congenital, and secondary glaucoma are much less common than chronic glaucoma.
- Severe eye pain, facial pain
- Loss of vision
- Cloudy vision with halos appearing around lights
- Red eye
- Fixed, nonreactive pupil
- Nausea and vomiting
- Gradual loss of peripheral vision
- Blurred or foggy vision
- Mild, chronic headaches
- Seeing rainbow-colored halos around lights
Note: Most people with chronic glaucoma have no symptoms until peripheral visual loss is severe
- Sensitivity to light
- Redness of the eye
- Corneal haziness
- Enlarged cornea
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:
- Retinal examination
- Intraocular pressure measurement by tonometry
- Visual field measurement
- Visual acuity
- Pupillary reflex response
- Slit lamp examination
- Optic nerve imaging (photographs of the interior of the eye)
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).
In recent years, many new medications have been introduced. Most cases of glaucoma will be treated with eye drops or combinations of several eye drops. The use of pills ot treat glaucoma is now much less common than in past years.
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.
Untreated chronic glaucoma can progress to blindness within 20 to 25 years. Early diagnosis and treatment have excellent success with preserving vision. Treatment prevents further loss, but does not bring back vision already lost.
The outcome for congenital glaucoma varies depending on the age when symptoms begin.
- Reduced vision
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.
Call for an appointment with your health care provider if you have risk factors for glaucoma and have not been screened for the condition.
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.
by David A. Scott, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.