Glaucoma

Definition
Glaucoma is a group of eye diseases that cause damage to the optic nerve due to a buildup of pressure inside the eyeball.

Anatomy
Normally, a clear fluid called aqueous humor flows into the eye through a space called the anterior chamber, located at the front of the eye. This fluid nourishes tissues in the eye. The fluid leaves the eye through a drain called the trabecular meshwork. This drain is located at the "angle" of the eye, where the cornea (the clear surface covering the eye) and iris (the colored part of the eye) meet



Causes/associated factors
Glaucoma is caused by aqueous humor buildup in the eye, usually due to problems with fluid drainage from the eye. As the fluid builds up, the pressure inside the eye increases, which damages the optic nerve and possibly other eye structures as well. Damage to the optic nerve can result in vision loss.
What causes glaucoma to develop is unknown, but risk factors include:

having high fluid pressure in the eye
a family history of glaucoma
being African American, especially over age 40
diabetes
myopia (nearsightedness)
being over age 60
high blood pressure
steroid use
certain eye injuries

Types of glaucoma
There are more than 40 types of glaucoma. Here are descriptions of four of the most common types.
Open-angle glaucoma
Open-angle glaucoma accounts for nearly 75 percent of all glaucoma cases. It's a slowly progressing chronic condition that can affect both eyes and is most common in nearsighted people. With this type of glaucoma, there's a blockage of the trabecular meshwork. The drain can get smaller with age or become clogged with a gradual deposit buildup. When there's a blockage, fluid can't leave the eye as quickly as it's produced. This buildup of fluid increases intraocular pressure.

Open-angle glaucoma may have vague symptoms or none at all, so you may not realize you're losing your vision until the late stages of the disease. Peripheral vision is lost before central vision. Periodic eye exams are the best way to detect open-angle glaucoma. Once nerve cells are destroyed and vision is lost, the damage is irreversible.

Angle-closure glaucoma
With this type of glaucoma, the iris is pushed against the trabecular meshwork, which blocks the drainage of fluid from the eye and causes high intraocular pressure. Sudden attacks of angle-closure glaucoma (acute angle-closure glaucoma, for example) can be precipitated by stress, dark environments (in which the pupil is fully dilated), and by the use of certain medications, such as antidepressants, antihistamines, and other cold and flu medications.

Angle-closure glaucoma can be chronic or acute (occur suddenly). The chronic type may cause vision damage without symptoms. Periodic eye exams are the best way to detect chronic angle-closure glaucoma.

Acute angle-closure glaucoma is a medical emergency. Unless it's treated quickly, permanent damage and blindness can occur. The following symptoms may indicate this type of glaucoma:

sudden onset of blurred vision
severe pain in or around the eye
colored halos around lights
nausea and vomiting
redness in the eye
headache
Some attacks may subside when the pupils constrict (by entering a well-lit room or sleeping, for example). If you notice any of the symptoms of acute glaucoma, however, seek medical attention right away.

Secondary glaucoma
Secondary glaucoma can develop after events such as an eye injury or trauma, or after the development of certain eye diseases that damage the eye structure. It may also develop as a result of steroid medication side effects or following eye surgery.

Congenital glaucoma
Congenital glaucoma is a rare childhood condition that appears soon after birth. Those with this condition have an abnormality of the drainage system for eye fluids within the eye. Because of this, the child may be sensitive to light and may tear excessively. A child with these symptoms or other eye problems should be taken to an ophthalmologist right away.


Diagnosis
Glaucoma is diagnosed with an eye exam. Using an instrument called an ophthalmoscope, the doctor can check out the optic nerve. The doctor may also do the following tests:
visual acuity, which measures the ability to see to various distances
tonometry, which measures eye pressure
perimetry, which tests visual fields
gonioscopy, which helps the doctor see the angle of the eye directly

Treatment
Although there is no cure for glaucoma, treatment can help prevent vision loss. Eyedrops, ointments, "wafers" (small strips of medication placed in the corner of the eyes) and oral medications can be used to treat open-angle glaucoma. These drugs work by reducing the pressure within the eye. Some commonly used drugs include timolol maleate, betaxolol, brimonidine tartrate (brand name Alphagan) and latanoprost (Xalatan).
If medication is not effective, then laser surgery may help prevent further damage to the optic nerve.

Argon laser trabeculoplasty may be used to treat open-angle glaucoma. This procedure alters the trabecular meshwork to help fluid pass through the blocked drainage system. Steroids may be prescribed for several days after surgery to reduce inflammation. Depending on individual circumstances, this procedure has a high success rate.

Laser iridotomy may be used to treat acute angle-closure glaucoma. An opening is made in the iris to let fluid drain and decrease intraocular pressure.

Cyclophotocoagulation is often used to treat advanced or aggressive cases of glaucoma. This procedure reduces fluid production in the eye by partially destroying the ciliary body or gland with a laser or freezing instrument. The ciliary body is an area just behind the base of the iris that is responsible for fluid production inside the eye.
Most laser procedures are done on an outpatient basis. Eyedrops are often used to numb the eye, so discomfort is minimal. After surgery there may be some eye irritation, but normal activities can usually be resumed in a day or two. Many people need to continue using glaucoma medications even after successful laser surgery.

If vision loss is rapid or medication or laser surgery doesn't help the condition, other types of surgery may be recommended.

Surgical procedures
To give fluid another way to leave the eye, the doctor may recommend a trabeculectomy. This procedure creates an alternate drainage system for the eye fluids to leave the inside of the eye. The procedure may be done in a hospital or on an outpatient basis. First, the doctor makes a space (called a filtering bleb) between the conjunctiva (outer lining of the eyelids and eyeball) and sclera (tough tissue that covers the white part of the eye). Next, a small hole may be cut in the iris to keep it from blocking the perforated sclera (a peripheral iridectomy). Finally, the scleral flap and the filtering bleb are sewn shut. The fluid that drains out of the new space is absorbed by the blood vessels in the conjunctiva.

Benefits of surgery: The surgery has a high success rate. If there is too much or too little fluid flow in the eye, an adjustment may be necessary. After surgery, anti-inflammatory eyedrops can help prevent scarring and cataract formation. Some people may need long-term drug therapy to keep the intraocular pressure low.

Risks of surgery: Complications of surgery are rare, but may include infection, bleeding, cataracts, changes in intraocular pressure or vision loss.

Recovery is often quick. To protect the eye, most people wear an eye patch for a few days after surgery. Your doctor may want you to avoid showering, swimming, driving or strenuous exercise for a short time. Contact your doctor right away if you notice redness or swelling in the eye or other side effects after surgery.


Complications
If glaucoma is left untreated, tunnel vision and blindness may develop within a few years. In fact, glaucoma is a leading cause of adult blindness in the United States. Once vision loss occurs, it cannot be reversed.

Pregnancy-specific information
Pregnancy is not considered a risk factor for glaucoma.

Senior-specific information
Conditions such as diabetes, eye surgery or cataracts may predispose older adults to glaucoma. Regular eye exams are recommended for older adults to detect eye disorders. Some experts recommend eye exams yearly or every two years beginning at age 60 or 65. Earlier or more frequent exams may be recommended for people at high risk of developing glaucoma.

Prevention
Early detection and treatment can prevent vision damage. Periodic eye exams are recommended by most health care professionals. If you're at high risk (you're African American, take corticosteroid medication on a long-term basis, have a parent or sibling with glaucoma, or have other factors that increase the risk of glaucoma), earlier or more frequent eye exams may be recommended. Consult your doctor about the best screening schedule for you.
If you have glaucoma, careful management of the condition can help preserve your vision. Here are a few tips.

Take any medications exactly as prescribed by your doctor.
If your condition changes or you experience side effects or new symptoms, call your doctor immediately.
Know what kind of glaucoma you have. Wear a medical ID bracelet or carry a medical emergency ID card to alert others of your condition.
Keep appointments for regularly scheduled exams and follow-up care.
You may also want to check out community support groups for people who have glaucoma.