Overview and Facts
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 * the most common type of glaucoma
- Secondary glaucoma
Symptoms and Types
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.
The front part of the eye is filled with a clear fluid called the aqueous humor. It is constantly made in the back of the eye then leaves the eye through channels in the front chamber of the eye. In angle-closure (acute) glaucoma, when the exit of the aqueous humor fluid is suddenly blocked, pressure increases and loss of vision and pain develop. Dilating eye drops and certain systemic medications may trigger an acute glaucoma attack if you are at risk.
In open-angle (chronic) 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.
Congenital glaucoma often runs in families (hereditary) and is present at birth.
Secondary glaucoma is caused by the use of drugs such as corticosteroids, several eye diseases, and systemic diseases.
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.
Diagnosis
When should you contact a doctor?
- If you have severe eye pain or a sudden loss of vision, especially loss of peripheral vision
- If you have risk factors for glaucoma and have not been screened for the condition
- Everyone over age 40 should have an eye examination at least once every 5 years, and more often if in a high-risk group.
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
Treatment and Care
Glaucoma treatments reduce intraocular pressure by improving aqueous outflow, reducing the production of aqueous, or both. Glaucoma can't be totally cured, and damage caused by the disease can't be reversed, but treatment and regular checkups can prevent visual loss in people with very early glaucoma. If visual loss has already occurred, treatment can slow or prevent further vision loss.
Eye drops
Glaucoma treatment often starts with medicated eye drops. Be sure to use the drops exactly as prescribed; otherwise, your optic nerve damage could get even worse. If your doctor prescribes more than one type of eye drop, make sure to ask how long to wait between applications. Because some of the eye drops are absorbed into your bloodstream, you may experience side effects unrelated to your eyes. To minimize this absorption, close your eyes for one to two 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.
The types of most commonly prescribed eye drops include:
- Beta blockers. These reduce the production of aqueous humor. Examples include levobunolol (Betagan), timolol (Betimol, Timoptic), betaxolol (Betoptic) and metipranolol (OptiPranolol). Possible side effects include difficulty breathing, slowed pulse, hair loss, lower blood pressure, impotence, fatigue, weakness, depression and memory loss. If you have asthma, bronchitis or emphysema, medications other than beta blockers may be recommended because beta blockers may worsen breathing problems. Your doctor also may recommend avoiding beta blockers if you're taking insulin for diabetes.
- Alpha-agonists. These reduce the production of aqueous humor and increase drainage. Examples include apraclonidine (Iopidine) and brimonidine (Alphagan). Possible side effects include fatigue; dizziness; red, itchy or swollen eyes; dry mouth; and allergic reactions.
- Carbonic anhydrase inhibitors. These also reduce the production of aqueous humor. Examples include dorzolamide (Trusopt) and brinzolamide (Azopt). Frequent urination and a tingling sensation in the fingers and toes are possible side effects, occurring more often with oral carbonic anhydrase inhibitors than with anhydrase inhibitor eye drops. If you have an allergy or sensitivity to sulfa drugs, don't use these medications unless there's no alternative.
- Prostaglandin-like compounds. These eye drops increase the outflow of aqueous humor. Examples include latanoprost (Xalatan), bimatoprost (Lumigan) and travoprost (Travatan). Possible side effects include mild reddening and stinging of the eyes and darkening of the iris, changes in the pigment of the eyelid skin, and blurred vision from swelling of the retina.
- Miotic or cholinergic agents. These also increase the outflow of aqueous humor. Examples include pilocarpine (Isopto Carpine, Pilopine) and carbachol (Isopto Carbachol). Possible side effects are 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 compounds, such as dipivefrin (Propine), also increase the outflow of aqueous humor. Possible side effects include red eyes, allergic reactions, palpitations, increased blood pressure, headache and anxiety.
Oral medications
If eye drops alone don't bring your eye pressure down to the desired level, your doctor may also prescribe an oral medication. Doctors commonly prescribe carbonic anhydrase inhibitors, such as acetazolamide (Diamox Sequels) and methazolamide (Neptazane), for glaucoma. Take these pills with meals to reduce side effects. Add bananas and apple juice to your diet to minimize the potassium loss caused by these medications.
Initially, carbonic anhydrase inhibitors may cause frequent urination and a tingling sensation in your fingers and toes. After several days, these symptoms usually disappear. Other possible side effects of carbonic anhydrase inhibitors include rashes, depression, fatigue, kidney stones, lethargy, stomach upset, a metallic taste in carbonated beverages, impotence and weight loss.
Neuroprotective drugs
Lowering the intraocular pressure provides only a partial solution when it comes to preserving vision in people with glaucoma. Ongoing clinical trials are evaluating certain drugs, such as brimonidine (Alphagan) and memantine (Namenda), to determine if they may help protect the optic nerve from damage associated with glaucoma.
Surgery
You may need surgery to treat glaucoma if you can't tolerate medications or if they're ineffective. 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 operation. Possible complications from glaucoma surgery may include infection, bleeding, abnormally high or low eye pressure, and, potentially, loss of vision. Having eye surgery may also speed up the development of cataracts. Most of these complications can be effectively treated.
Surgeries used to treat glaucoma include:
- Laser surgery. In the last couple of decades, a procedure called trabeculoplasty (truh-BEK-u-lo-plas-tee) has had an increased role in treating open-angle glaucoma. After giving you an anesthetic eye drop, the doctor uses a high-energy laser beam to open clogged drainage canals and help aqueous humor drain more easily from the eye.
This is an office procedure lasting 10 to 20 minutes, and you can usually resume normal activities without discomfort. The doctor will need to check your eye pressure several times in the following weeks. 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. After time, however, intraocular pressure may begin to increase.
- Filtering surgery. If eye drops and laser surgery aren't effective in controlling your eye pressure, you may need an operation called a filtering procedure, usually in the form of a trabeculectomy (truh-bek-u-LEK-tuh-me).
This procedure is done in a hospital or an outpatient surgery center. You'll receive eye drops, a medication to help you relax and usually an injection of anesthetic to numb your eye. Using delicate instruments under an operating microscope, your 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 trabeculectomy leaves no open hole in your eye. This procedure works best if you haven't had any previous eye surgery. Your doctor will check your eye during several follow-up visits and you'll need to use antibiotic and anti-inflammatory eye drops to fight infection and scarring of the newly created drainage opening.
A new procedure performed within the eye removes a targeted strip of trabecular meshwork with a tiny electrocauterizing tool. The tool is introduced into the eye's drainage canal through a 1/16-inch (1.5-millimeter) incision at the edge of the cornea. A predetermined section of the trabecular meshwork can be removed from the inside of the eye with this instrument. Early reports indicate this procedure is effective and associated with few complications.
Drainage implants. Another type of operation, called drainage implant surgery, may be an option for people with secondary glaucoma or for children with glaucoma. Drainage implant surgery takes place in a hospital or an outpatient clinic, and consists of a doctor inserting 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 eye drops for several weeks to fight infection and scarring.
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. You'll also likely have an iridotomy, a laser procedure that creates a small hole in your iris so that aqueous humor can pass into the trabecular meshwork. Many doctors recommend an iridotomy on the other eye at a later date because of the high risk that its drainage angle will close as well.
If left untreated, glaucoma will cause progressive vision loss, typically in these stages:
- Blind spots in your peripheral vision
- Tunnel vision
- Total blindness