| What is glaucoma? |
Glaucoma is sometimes called the silent thief, slowly stealing your sight before you realize anything's wrong. The most common form of glaucoma develops gradually, giving no warning signs. Many people aren't even aware they have an eye problem until their vision is extensively damaged. Glaucoma is the second most common cause of vision loss in the United States. It affects approximately 3 million Americans.
Glaucoma is not just one disease but is a group of them. The common feature of these diseases is that abnormally high pressure inside the eyeball damages the optic nerve. The optic nerve is a bundle of more than a million nerve fibers at the back of your eye. It's like a big electric cable made up of thousands of individual wires carrying the images you see from the retina to your brain. Blind spots develop in your visual field when the optic nerve deteriorates, starting with your peripheral (side) vision. If left untreated glaucoma may lead to blindness in both eyes.
Fortunately, only a small percentage of people with the disease lose their sight. Recent medical advances have made it easier to diagnose and treat glaucoma. And if detected and treated early, glaucoma need not cause even moderate vision loss. But it does require regular monitoring and treatment for the rest of your life.
| Signs and Symptoms |
Glaucoma occurs in several types. The differences have to do with what's causing the pressure in the eye, which can lead to damage of the optic nerve. Signs and symptoms vary depending on the type of glaucoma.
Primary open-angle glaucoma progresses with few or no symptoms until the condition reaches an advanced stage. As increased eye pressure continues to damage your optic nerve, you lose more and more of your peripheral vision. Open-angle glaucoma usually affects both eyes, although at first you may have symptoms in just one eye. Other symptoms include:
- Sensitivity to light and glare
- Trouble differentiating between varying shades of light and dark
- Trouble with night vision
- Blurred vision
- Halos around lights
- Reddening of the eye
- Headache
- Severe eye pain
- Nausea and vomiting
- Hardness of the affected eye
| Causes |
Internal pressure in your eye, called intraocular pressure, allows your eye to hold its shape and function properly. Intraocular pressure is like air in a balloon — too much pressure inside the balloon affects its shape and may even cause it to pop. In the case of your eye, too much pressure can damage the optic nerve.
Fluids inside your eye help maintain the intraocular pressure. These fluids are the vitreous, which fills the vitreous cavity, at the back of your eye, and the aqueous humor, which fills the anterior chamber, at the front of your eye. Aqueous humor is continuously produced and circulated through the anterior chamber before draining out of your eye. This continuous flow of fluid nourishes the lens and the cornea and removes unwanted debris. A healthy eye produces aqueous humor at the same rate that it drains fluid, thus maintaining a normal pressure.
Aqueous humor exits your eye through a drainage system located at the angle formed where the iris and the cornea meet. Here it passes through a sieve-like system of spongy tissue called the trabecular meshwork and drains into a channel called Schlemm's canal. The fluid then merges into your bloodstream.
When the drainage system doesn't function properly — for example, if the trabecular meshwork becomes clogged — the aqueous humor can't flow at its normal rate and pressure builds within your eye. For reasons that doctors don't completely understand, the increased eye pressure gradually damages the nerve fibers that make up the optic nerve.
Types of glaucoma
Glaucoma occurs in several types. The differences have to do with what's causing the fluid blockage that builds pressure in your eye.
- Primary open-angle. Primary open-angle glaucoma, also called chronic open-angle glaucoma,
accounts for most cases of the disease. Although the drainage angle formed by the cornea and the iris
remains open, the aqueous humor drains too slowly. This leads to fluid backup and a gradual buildup of
pressure within your eye. Damage to the optic nerve is so slow and painless that a large portion of
your vision can be lost before you're even aware of a problem.
The cause of primary open-angle glaucoma remains unknown. It may be that the aqueous humor drains or is absorbed less efficiently with age, but not all older adults get this form of glaucoma. - Angle-closure. Angle-closure glaucoma, also called closed-angle glaucoma, is a less common
form of the disease. It occurs when the drainage angle formed by the cornea and the iris closes or
becomes blocked. The aqueous humor can't exit through the trabecular meshwork, resulting in an
increase in eye pressure. Angle-closure glaucoma can be chronic (progressing gradually) or acute
(coming on suddenly).
Most people with this type of glaucoma have a very narrow drainage angle, which may be an abnormality from birth. Angle-closure glaucoma is more common among farsighted people, who tend to have smaller eyes that can narrow the angle. Normal aging also may cause angle blockage. As you get older, your lens becomes larger, pushing your iris forward and narrowing the space between the iris and the cornea.
If you have a narrow drainage angle and your pupils become widely dilated, the angle may close and cause a sudden increase in eye pressure. This attack of acute angle-closure glaucoma requires immediate treatment. Although an acute attack often affects only one eye, the other eye is at risk of an attack as well.
Several factors can cause your pupils to dilate, including darkness or dim light, stress or excitement, and certain medications. These medications include antihistamines, tricyclic antidepressants and eyedrops used to dilate your pupils, which may not cause the angle to close until several hours after you put in the drops.
Acute angle-closure glaucoma is a medical emergency that can cause vision loss within hours of its onset. Without treatment the eye can become blind in as little as 1 or 2 days. - Secondary. Both open-angle and angle-closure glaucoma can be primary or secondary
conditions. They're called primary when the cause of the condition is unknown. They're called
secondary when the condition can be traced to a known cause, such as an injury or an eye disease.
Secondary glaucoma may be caused by a variety of medical conditions, medications, physical injuries,
and eye abnormalities or deformities. Infrequently eye surgery can cause secondary glaucoma.
- Low-tension. Low-tension glaucoma is an unusual and poorly understood form of the disease. In this form, eye pressure remains within a normal range but the optic nerve is damaged nevertheless. Why this happens is unknown, although some experts believe that people with low-tension glaucoma may have an abnormally fragile optic nerve or a reduced blood supply to the optic nerve, caused by a condition such as closed arteries (atherosclerosis). Under these circumstances even normal pressure on the optic nerve is enough to cause damage.
Doctors don't completely understand the underlying causes of glaucoma. Open-angle glaucoma may have a genetic link. That is, a defect in one or more genes may cause the disease. People with a family history of glaucoma are more likely to develop it themselves. However, the exact genetic defects responsible for its occurrence haven't been identified.
Other factors appear to contribute to the disease, but doctors don't know for sure what these factors are and the relationships among them. Although glaucoma is normally associated with increased eye pressure, people with normal or low eye pressure can experience vision loss. And people with higher-than-normal eye pressure may never experience optic nerve damage.
Doctors have debated for many years about how damage to the optic nerve occurs. One theory holds that the pressure of backed up aqueous humor causes structural damage and ultimately death to the nerve fibers. Another theory suggests that nerve fibers die when small blood vessels that feed the optic nerve become blocked or when the blood supply is disrupted.
The cause of decreased drainage through the trabecular meshwork also presents a puzzle. The changes that slow drainage may be a result of normal aging, yet not all older adults develop glaucoma.
| Risk Factors |
If your intraocular pressure is higher than what's considered normal, you're at increased risk of developing glaucoma. Yet most people with slightly elevated intraocular pressure don't develop the disease. This makes it difficult to predict who will get glaucoma.
Certain other factors increase your risk. Because chronic forms of glaucoma can destroy vision before any symptoms are apparent, be aware of these factors:
- Age. Open-angle glaucoma is rare before age 40. The risk of developing glaucoma nearly
doubles every 10 years after age 50. Approximately 14 percent of people in the United States who are
at least age 80 have the disease. Primary open-angle glaucoma is most common in older adult women.
- Race. In the United States, blacks are three to four times more likely to get glaucoma than
are whites, and they are six times more likely to suffer permanent blindness as a result. The reasons
for these differences aren't known, but blacks may be more susceptible to damage to the optic nerve,
or they may not respond to current treatments as well as whites do. Asian-Americans, particularly
people of Vietnamese descent, also are at higher risk. Japanese-Americans are more prone to develop
low-tension glaucoma.
- Family history of glaucoma. If one of your parents has glaucoma, you have about a 20
percent chance of developing the disease. If you have a sibling with the disease, your chance of
getting it is about 50 percent.
- Medical conditions. If you have diabetes, your risk of developing glaucoma is about three
times greater than that of people who don't have diabetes. A history of high blood pressure or heart
disease also can increase your risk. Other risk factors include retinal detachment, eye tumors and eye
inflammations such as chronic uveitis and iritis. Previous eye surgery may trigger secondary glaucoma.
- Physical injuries. Severe trauma, such as being hit in the eye, can result in increased eye
pressure. Injury can also dislocate the lens, closing the drainage angle.
- Nearsightedness. Severe nearsightedness increases the risk of developing glaucoma. An
extensive study of eye health found that nearsighted people had a two to three times higher risk of
developing glaucoma than did people who were not nearsighted.
- Prolonged corticosteroid use. Using corticosteroids for prolonged periods of time puts you
at risk of getting secondary glaucoma.
- Eye abnormalities. Structural abnormalities of the eye can lead to secondary glaucoma. For example, pigmentary glaucoma is a form of secondary glaucoma caused by pigment granules being released from the back of the iris. These granules can block the trabecular meshwork.
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| When to Seek Medical Advice |
Primary open-angle glaucoma gives few warning signs until permanent damage has already occurred. That's why regular eye exams are the key to detecting glaucoma early enough for successful treatment. It's best to have routine eye checkups every 2 to 4 years after age 40 and every 1 to 2 years after age 65. Don't wait for symptoms of any kind to occur. If you have one or more risk factors for glaucoma, talk to your doctor about scheduling regular eye exams. Some tests can be performed by your doctor, but others need to be done by an eye care specialist.
In addition, be alert for signs of an acute angle-closure glaucoma attack, such as a severe headache or pain in your eye or eyebrow, nausea, blurred vision or rainbow halos around lights. If you experience any of these symptoms, seek immediate care at your local hospital emergency room.
If you've received a diagnosis of glaucoma, establish a regular schedule of examinations with your doctor to be sure your treatment is helping maintain a safe pressure of fluid in your eyes.
| Screening and Diagnosis |
If your doctor suspects that you have glaucoma, he or she may perform a series of tests to detect any signs of damage. Tests include:
- Tonometry. Tonometry is a simple, painless procedure that measures your intraocular
pressure. It is usually the initial screening test for glaucoma. Two common techniques are air-puff
tonometry and applanation tonometry. Air-puff tonometry uses a puff of air to measure the amount of
force needed to indent your cornea. An applanation tonometer is a sophisticated device that's usually
fitted to a slit lamp. Slit lamps use an intense line of light — a slit — providing illumination of
the cornea, iris, lens and anterior chamber, and allowing your doctor a good view of these structures.
In tonometry, your doctor numbs your eyes with drops and has you sit at the slit lamp, where a small
flat-tipped cone pushes lightly against your eyeball. The force required to flatten (applanate) a
small area of your cornea translates into a measure of your intraocular pressure.
Normal eye pressure ranges from 10 to 22 millimeters of mercury (mm Hg). Doctors consider anyone with eye pressure over 23 mm Hg to be at risk of developing glaucoma and in need of careful monitoring for early signs of glaucoma. People with intraocular pressure greater than 30 mm Hg are at high risk. - Test for optic nerve damage. To check the fibers in your optic nerve, your eye doctor uses
an instrument called an ophthalmoscope, which enables him or her to look directly through the pupil to
the back of your eye. Your doctor may also use laser light and computers to create a three-dimensional
image of your optic nerve. This can reveal slight changes that may indicate the beginnings of
glaucoma.
- Visual field test. To check how your visual field has been affected by glaucoma, the doctor
uses a perimetry test. One method, known as tangent screen perimetry, requires you to look at a screen
with a target in the center. Your eye doctor manipulates a small object on a wand at different
locations in your visual field. You indicate whenever you see the object come into view. By repeating
this process over and over again, the doctor can map your entire visual field.
- Other tests. To distinguish between open-angle glaucoma and angle-closure glaucoma, your eye doctor may use a technique called gonioscopy (go-ne-OS-kuh-pe), in which a special lens is placed on the eye to inspect the drainage angle. Another test, tonography, can measure how fast fluid drains through the trabecular meshwork.
| Treatment |
If your doctor determines that you have elevated intraocular pressure, an excavated optic disk and loss of visual field, you'll likely be treated for glaucoma. If you have only slightly elevated eye pressure, an undamaged optic nerve and no visual field loss, you may not need treatment, but your doctor may advise more frequent examinations to detect any future changes. If you have signs of optic nerve damage and visual field loss, even if your eye pressure is in the normal range, you may need treatment to lower eye pressure further, which may help slow the progression of glaucoma.
Glaucoma can't be cured, and damage caused by the disease can't be reversed. But with treatment, glaucoma can be controlled. Eyedrops, oral medications and surgical procedures can prevent or slow further damage.
Having glaucoma means you'll need to continue treatment for the rest of your life. Because the disease can progress or change without your being aware of it, your treatment may need to be changed over time. Regular checkups and adherence to a treatment plan may seem burdensome, but they're essential to prevent vision loss.
Preventing further damage to the optic nerve and continued loss of visual field may be accomplished by keeping your eye pressure under control. Your eye doctor may focus on lowering your intraocular pressure to a level that's unlikely to cause further optic nerve damage. This level is often referred to as the target pressure and will probably be a range rather than a single number. Target pressure differs for each person, depending on the extent of the damage and other factors. Your target pressure may change over the course of your lifetime.
Medications are the most common early treatment for glaucoma. Standard practice has been to move on to surgery if medications are ineffective. However, surgery is an option as a safe and effective initial treatment.
Eyedrops
Glaucoma treatment often starts with medicated eyedrops. Doctors prescribe several types of drops. Be sure to use the drops exactly as prescribed to control your intraocular pressure. Skipping even a few doses can cause damage to the optic nerve to worsen. Some drops need to be applied several times each day, and others must be used just once a day. Inform your doctor of all other medications you're taking, to avoid any undesirable drug interactions.
Because some of the eyedrops are absorbed into your bloodstream, you may experience side effects unrelated to your eyes. To minimize this absorption, close your eyes for 1 to 2 minutes after putting the drops in. Press lightly at the corner of your eye near your nose to close the tear duct, and wipe off any unused drops from your eyelid. Your doctor may prescribe more than one type of eyedrop. If you're using more than one, wait 5 to 10 minutes between applications.
The types of eyedrops that doctors most commonly prescribe include:
- Beta blockers. These reduce the production of aqueous humor. Examples include levobunolol
(AKBeta, Betagan), timolol (Betimol, Timoptic,), carteolol (Ocupress), betaxolol (Betoptic) and
metipranolol (OptiPranolol). Possible side effects include difficulty breathing, slowed pulse, hair
loss, decreased blood pressure, impotence, fatigue, weakness, depression and memory loss. If you have
asthma, bronchitis or emphysema, or if you have diabetes and use insulin, beta blockers shouldn't be
used unless no alternative is possible, and then only with great care.
- Alpha-adrenergic agents. These reduce the production of aqueous humor. Examples include
apraclonidine (Iopidine) and brimonidine (Alphagan). Possible side effects include increased blood
pressure, tremors, headache, anxiety, red and itchy eyes, dry mouth and allergic reactions.
- Carbonic anhydrase inhibitors. These medications, which include dorzolamide (Trusopt),
reduce the amount of aqueous humor. Possible side effects include a bad taste in the mouth. Frequent
urination and a tingling sensation in the fingers and the toes are common when a carbonic anhydrase
inhibitor is taken orally but rare when it is taken as drops. If you're allergic to sulfa drugs, this
type of medication shouldn't be used unless no alternative is possible, and then only with great care.
- Prostaglandin analogues. These eyedrops increase the outflow of aqueous humor. These
hormone-like substances, which include latanoprost (Xalatan), may be used in conjunction with a drug
that reduces production of aqueous humor. Possible side effects include mild reddening and stinging of
the eyes and darkening of the iris and the eyelid skin.
- Prostamides. These include bimatoprost (Lumigan). They increase the outflow of aqueous humor. Possible side effects include mild to moderate reddening of the eyes and eyelash growth.
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Other eyedrops that are rarely used include:
- Miotics. These increase the outflow of aqueous humor. Examples include pilocarpine (Isopto
Carpine, Pilocar). Possible side effects include pain around or inside the eyes, brow ache, blurred or
dim vision, nearsightedness, allergic reactions, a stuffy nose, sweating, increased salivation and
occasional digestive problems.
- Epinephrine compounds. These increase the outflow of aqueous humor. Examples include epinephrine (Epifrin, Eppy/N). Possible side effects include red eyes, allergic reactions, palpitations, high blood pressure, headache and anxiety.
If eyedrops alone don't bring your eye pressure down to the desired level, your doctor may also prescribe oral medication. The most common oral medications for glaucoma are carbonic anhydrase inhibitors. These include acetazolamide (Diamox, Storzolamide), dichlorphenamide (Daranide) and methazolamide (Neptazane). Take these pills with meals to reduce side effects. You can help to minimize the potassium loss that these medications can cause by adding bananas and apple juice to your diet.
When you first start taking these oral medications, you may experience a frequent need to urinate and a tingling sensation in the fingers and the toes. These symptoms often disappear after a few days. Other possible side effects of carbonic anhydrase inhibitors include rashes, depression, fatigue, lethargy, stomach upset, a metallic taste in carbonated beverages, impotence and weight loss. Kidney stones also can occur.
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Surgery
You may need surgery to treat glaucoma if you can't tolerate medications or they're ineffective. Doctors use several types of surgery to treat glaucoma:
- Laser surgery. In the last couple of decades, a procedure called trabeculoplasty
(truh-BEK-u-lo-plas-te) has been used increasingly in the treatment of open-angle glaucoma. The doctor
uses a high-energy laser beam to shrink part of the trabecular meshwork, which causes other parts of
the meshwork to stretch and open up. This helps aqueous humor drain more easily from the eye.
This type of laser surgery is an office procedure that takes 10 to 20 minutes. You'll be given an anesthetic eyedrop, seated at a slit lamp and fitted with a special lens on your eye. The doctor aims the laser through the lens at the trabecular meshwork and applies burns to it. You will see bright flashes of light.
After the surgery you can immediately resume normal activities without discomfort. The doctor will check your eye pressure 1 to 2 hours after the procedure and several times in the following weeks. He or she may prescribe anti-inflammatory eyedrops for you to use for a few days following trabeculoplasty. It may take a few weeks before the full effect of the surgery becomes apparent.
In almost all cases, laser surgery for glaucoma initially lowers intraocular pressure. However, its effects may wear off over time. Studies show that eye pressure rises in many people 2 to 5 years after they receive the laser treatment. - Conventional surgery. If eyedrops and laser surgery aren't effective in controlling your
eye pressure, you may need an operation called a trabeculectomy (truh-bek-u-LEK-tuh-me). This
procedure is done in a hospital or an outpatient surgery center. You'll receive medication to help you
relax and eyedrops and an injection of anesthetic to numb your eye. Using delicate instruments under
an operating microscope, the surgeon creates an opening in the sclera — the white of your eye — and
removes a small piece of the trabecular meshwork. The aqueous humor can now freely leave the eye
through this hole. As a result your eye pressure will be lowered. The hole is covered by the
conjunctiva, so there's not an open hole in your eye.
Your doctor will check your eye in several follow-up visits. You'll use antibiotic and anti-inflammatory eyedrops for some time after the operation to fight infection and scarring of the newly created drainage opening. Scarring is a particular problem for young adults, blacks and people who have had cataract surgery. This procedure works best if you haven't had any previous eye surgery.
Although glaucoma surgery may preserve current vision, it can't restore already lost vision. Sometimes a single surgical procedure may not lower eye pressure enough, in which case you'll need to continue using glaucoma drops or have another trabeculectomy operation. - Drainage implants. Another type of operation, called drainage implant surgery, may be
performed on people with secondary glaucoma or on children with glaucoma.
Like the trabeculectomy, drainage implant surgery is performed at a hospital or an outpatient clinic. You'll be given medication to help you relax and eyedrops and an anesthetic to numb the eye. Then the doctor inserts a small silicone tube in your eye to help drain aqueous humor.
After the surgery you'll wear an eye patch for 24 hours and use eyedrops for several weeks to fight infection and scarring. Your doctor will check your eyes several times in the weeks that follow.
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Treating acute angle-closure glaucoma
Acute angle-closure glaucoma is a medical emergency. When you come in with this condition, doctors may administer several medications to reduce eye pressure as quickly as possible. Once your eye pressure is under control, you'll likely have an operation called iridotomy (ir-ih-DOT-uh-me). In this procedure the doctor uses a laser beam to create a small hole in your iris that allows aqueous humor to flow more freely into the anterior chamber. Many doctors recommend an iridotomy on the other eye at a later date because of the high risk that it too will have an attack within the next few years.
| Prevention |
There's no known way to prevent glaucoma, but regular checkups can help detect the disease in its early stages before irreversible damage has occurred. As a general rule, have eye exams every 2 to 4 years if you're between the ages of 40 and 65, and every 1 to 2 years if you're older than 65.
Your doctor may recommend more frequent monitoring if you're at increased risk of developing glaucoma. You may also need even more frequent checkups if you have received a diagnosis of abnormally high intraocular pressure or have a history of serious eye injury.
| Self-Care |
The most important thing you can do if you have glaucoma is take your medications exactly as prescribed. Frequent eye exams will help your doctor monitor your eye pressure and keep you and your doctor aware of any changes in your vision.
Other self-care tips:
- Maintain a healthy diet. Vitamins and minerals that are important for the eyes include
vitamin A, vitamin C, vitamin E, zinc and copper. Drink fluids in small amounts over the course of a
day. Drinking a quart or more of any liquid within a short time may increase eye pressure. Limit
caffeine to low or moderate levels.
- Exercise regularly. Studies show that people with open-angle glaucoma who exercise
regularly — at least three times a week — can reduce their eye pressure by an average of 20 percent.
However, angle-closure glaucoma isn't affected by exercise, and people with pigmentary glaucoma, a
form of secondary glaucoma, may experience increased eye pressure after exercise. Talk to your doctor
about an appropriate exercise program.
- Steer clear of herbal remedies. A number of herbal supplements, such as bilberry, are
advertised as glaucoma remedies. Bilberry is not effective in preventing or treating glaucoma. Be
cautious about herbal supplements and discuss them with your doctor before trying them.
- Find healthy ways to cope with stress. Stress can trigger an attack of acute angle-closure
glaucoma. Relaxation techniques, such as meditation and progressive muscle relaxation, may be helpful
in dealing with stress.
- Wear sunglasses with full ultraviolet protection. Whenever you're out in the sun, even if
only for a few minutes, wear sunglasses that block ultraviolet (UV) light.
- Wear proper eye protection. Eye trauma can result in increased eye pressure. Use safety glasses or goggles when you play sports, use tools or machinery, or work with chemicals.
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— September 10, 2002 —