Glaucoma refers to a group of disorders that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain.

Glaucoma is the second most common cause of blindness in the United States. There are four major types of glaucoma:

• Angle-closure (acute) glaucoma
• Congenital glaucoma
• Open-angle (chronic) 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. Open-angle (chronic) glaucoma is by far the most common type of glaucoma.

The front part of the eye is filled with a clear fluid called the aqueous humor. This fluid is constantly made in the back of the eye. It leaves the eye through channels in the front (anterior) chamber of the eye in an area called the anterior chamber angle, or simply the angle.

Angle-closure (acute) glaucoma occurs when the exit of the aqueous humor fluid is suddently blocked. This causes a quick, severe, and painful rise in the pressure within the eye (intraocular pressure). Angle-closure glaucoma is an emergency. This is very different from open-angle glaucoma, which painlessly and slowly damages vision.

If you have had acute glaucoma in one eye, you are at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment.

Dilating eye drops and certain systemic medications may trigger an acute glaucoma attack if you are at risk.

Congenital glaucoma often runs in families (hereditary). It is present at birth, and is the result of the abnormal development of the fluid outflow channels in the eye.

In open-angle glaucoma, the cause is essentially unknown. An increase in eye pressure pushes on the junction of the optic nerve and the retina at the back of the eye, reducing the blood supply to the optic nerve.

Open-angle glaucoma tends to run in families. Your risk is higher if you have a parent or grandparent with open-angle glaucoma. People of African descent are at particularly high risk for this disease.

Secondary glaucoma is caused by:

• Drugs such as corticosteroids
• Eye diseases such as uveitis
• Systemic diseases

OPEN-ANGLE

• Gradual loss of peripheral (side) vision
• Most people have no symptoms until they lose vision

ANGLE-CLOSURE

• Decreased or cloudy vision
• Nausea and vomiting
• Pupil does not react to light
• Red eye
• Severe eye pain, facial pain
• Swelling of the eye

CONGENITAL

• Cloudiness of the front of the eye
• Enlargement of one eye or both eyes
• Red eye
• Sensitivity to light
• Tearing

An examination of the eye may be used to diagnose glaucoma. However, checking the intraocular pressure alone (tonometry) is not enough because eye pressure changes. The doctor will need to examine the inside of the eye by looking through the pupil, often while the pupil is dilated.

Usually the doctor will perform a complete examination of the eyes.

Tests may include:

• Gonioscopy (use of a special lens to see the outflow channels of the angle)
• Intraocular pressure measurement by tonometry
• Optic nerve imaging (photographs of the interior of the eye)
• Pupillary reflex response
• Refraction
• Retinal examination
• Slit lamp examination
• Visual acuity
• Visual field measurement

The objective of treatment is to reduce intraocular pressure. Depending on the type of glaucoma, this is achieved with medications or by surgery.

Open-angle glaucoma treatment:

Most people with glaucoma can be treated successfully with eye drops. In the past, eye drops for glaucoma caused blurring of vision, but most eye drops used today have few side effects. Your doctor will look at your medical history and determine the best drops for you. You may need more than one type of drop. Some patients may also be treated with pills to lower pressure in the eye. Newer drops and pills are being developed that directly protect the optic nerve from glaucoma damage.

Some patients will need other forms of treatment, such as a laser treatment, to help open the fluid outflow channels. This procedure is usually painless. Others may need traditional surgery to open a new outflow channel.

Angle-closure glaucoma treatment:

Acute angle-closure attack is a medical emergency. Blindness will occur in a few days if it is not treated. Drops, pills, and medicine given through a vein (by IV) are used to lower pressure. Some people also need an emergency operation, called an iridotomy. This procedure uses a laser to open a new channel in the iris. The new channel relieves pressure and prevents another attack.

Congenital glaucoma:

This form of glaucoma is almost always treated with surgery to open the outflow channels of the angle. This is done while the patient is asleep and feels no pain (with anesthesia).

Open-angle glaucoma:

You can manage open-angle glaucoma and almost always preserve your vision, but the condition cannot be cured. It's important to carefully follow up with your doctor. With good care, most patients with open-angle glaucoma will not lose vision.

Angle-closure glaucoma:

Rapid diagnosis and treatment of an attack is the key element to preserving vision. Seek emergency care if you have the symptoms of angle-closure attack.

Congenital glaucoma:

Early diagnosis and treatment is important. If surgery is done early enough, many patients will have no future problems.

Call your health care provider if you have severe eye pain or a sudden loss of vision, especially loss of peripheral 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 way to prevent open-angle glaucoma, but you can prevent vision loss from the condition. Early diagnosis and careful management are the keys to preventing vision loss.

Most people with open-angle glaucoma have no symptoms. Everyone over age 40 should have an eye examination at least once every 5 years, and more often if in a high-risk group. Those in high-risk groups include people with a family history of open-angle glaucoma and people of African heritage.

People at high risk for acute glaucoma may opt to undergo iridotomy before having an attack. Patients who have had an acute episode in the past may have the procedure to prevent a recurrence.

Burr JM, Mowatt G, Hern??ndez R, Siddiqui MA, Cook J, Lourenco T, et al. The clinical effectiveness and cost-effectiveness of screening for open angle glaucoma: a systematic review and economic evaluation. Health Technol Assess. 2007 Oct;11(41):iii-iv, ix-x, 1-190.

Vass C, Hirn C, Sycha T, Findl O, Bauer P, Schmetterer L. Medical interventions for primary open angle glaucoma and ocular hypertension. Cochrane Database Syst Rev. 2007 Oct 17;(4):CD003167.