Glaucoma

Glaucoma a group of conditions resulting in optic nerve damage, which diminishes sight. Abnormally high pressure inside your eye (intraocular pressure) usually, but not always, causes this damage.
Glaucoma is the second leading cause of blindness. Sometimes called the silent thief of sight, glaucoma can damage your vision so gradually you don’t notice any loss of vision until the disease is at an advanced stage. The most common type of glaucoma, primary open-angle glaucoma, has no noticeable signs or symptoms except gradual vision loss.
Early diagnosis and treatment can minimize or prevent optic nerve damage and limit glaucoma-related vision loss. It’s important to get your eyes examined regularly, and make sure your eye doctor measures your intraocular pressure.

It’s best to have routine eye checkups every two years if you’re between 18-60 years old, and every year if you’re older than 60.

Glaucoma Causes

Increased intraocular pressure is usually associated with the optic nerve damage that characterizes glaucoma. This pressure comes from a buildup of aqueous humor, a fluid naturally and continuously produced in the front of your eye.

Aqueous humor normally exits your eye through a drainage system at the angle where the iris and the cornea meet. When the drainage system doesn’t function properly, the aqueous humor can’t filter out of the eye at its normal rate, and pressure builds within your eye.

In primary open-angle glaucoma, the drainage angle formed by the cornea and the iris remains open, but the microscopic drainage channels in the angle (called the trabecular meshwork) are partially obstructed, causing the aqueous humor to drain out of the eye too slowly. This leads to fluid backup and a gradual increase of pressure within your eye. Damage to the optic nerve is painless and so slow that a large portion of your vision can be lost before you’re even aware of a problem. The exact cause of primary open-angle glaucoma remains unknown.

Angle-closure glaucoma, also called closed-angle glaucoma, occurs when the iris bulges forward to narrow or block the drainage angle formed by the cornea and the iris. As a result, aqueous fluid can no longer access the trabecular meshwork at the angle, so the eye pressure increases abruptly. Angle-closure glaucoma usually occurs suddenly (acute angle-closure glaucoma), but it can also occur gradually (chronic angle-closure glaucoma.)
Many people who develop closed-angle glaucoma have an abnormally narrow drainage angle to begin with. This narrow angle may never cause any problems, so it may go undetected for life.

If you have a narrow drainage angle, sudden dilation of your pupils may trigger acute angle-closure glaucoma. Pupils become dilated in response to darkness, dim light, stress, excitement and certain medications. These medications include antihistamines, such as desloratadine (Clarinex) and cetirizine (Zyrtec); tricyclic antidepressants, such as doxepin (Sinequan) and protriptyline (Vivactil); and eyedrops used to dilate your pupils for a thorough eye exam.

Another form of the disease, poorly understood but not uncommon, is low-tension glaucoma. In this form, optic nerve damage occurs even though eye pressure stays within the normal range. Why this happens is unknown. Some experts believe that people with low-tension glaucoma may have an abnormally sensitive optic nerve or a reduced blood supply to the optic nerve caused by atherosclerosis — an accumulation of fatty deposits (plaques) in the arteries — or another condition limiting circulation. Under these circumstances, even normal pressure on the optic nerve seems to be enough to cause damage.

Pigmentary glaucoma, a type of glaucoma that can develop in young to middle-aged adults, is associated with a dispersion of pigment granules within the eye. The pigment granules appear to arise from the back of the iris. When the granules accumulate on and in the trabecular meshwork, they can interfere with the outflow of aqueous and cause a rise in pressure. Physical activities, such as jogging, sometimes stir up the pigment granules, depositing them on the trabecular meshwork and causing intermittent pressure elevations. This type of glaucoma can usually be easily diagnosed by your ophthalmologist.

Glaucoma signs and symptoms

The most common types of glaucoma — primary open-angle glaucoma and acute angle-closure glaucoma — have completely different symptoms.

Primary open-angle glaucoma signs and symptoms include:

  • Gradual loss of peripheral vision, usually in both eyes
  • Tunnel vision in the advanced stages

Acute angle-closure glaucoma signs and symptoms include:

  • Severe eye pain
  • Nausea and vomiting (accompanying the severe eye pain)
  • Sudden onset of visual disturbance, often in low light
  • Blurred vision
  • Halos around lights
  • Reddening of the eye

Both open-angle and angle-closure glaucoma can be primary or secondary conditions. They’re called primary when the cause is unknown and secondary when the condition can be traced to a known cause, such as eye injury, inflammation, tumor, or advanced cataract or diabetes. In secondary glaucoma, the signs and symptoms can include those of the primary condition as well as typical glaucoma symptoms.

In addition, be aware that a severe headache or pain in your eye or eyebrow, nausea, blurred vision, or rainbow halos around lights may be the symptoms of an acute angle-closure glaucoma attack. If you experience two or more of these symptoms together, seek immediate care at an emergency room or an eye doctor’s (ophthalmologist’s) office.

Diagnosis of glaucoma:

  • Tonometry. Tonometry is a simple, painless procedure that measures your intraocular pressure, after numbing your eyes with drops. It is usually the initial screening test for glaucoma.
  • Test for optic nerve damage. To check the fibers in your optic nerve, your eye doctor uses an instrument that enables him or her to look directly through the pupil to the back of your eye. This can reveal slight changes that may indicate the beginnings of glaucoma.
  • Photographs and drawings of the optic nerve. These images may be useful for documenting the severity of the condition.
  • Visual field test. To check whether your visual field has been affected by glaucoma, your doctor uses a special test to evaluate your peripheral (side) vision.
  • Pachymetry. Your eyes are numbed for this test, which determines the thickness of each cornea, an important factor in diagnosing glaucoma. If you have thick corneas, your eye pressure reading may read artificially high even though you may not have glaucoma. Similarly, people with thin corneas can have normal pressure readings and still have glaucoma.
  • Other tests. To distinguish between open-angle glaucoma and angle-closure glaucoma, your eye doctor may use a technique called gonioscopy in which he or she places a special lens on your eye to inspect the drainage angle. Another test, tonography, can measure how quickly fluid drains from your eye.

Glaucoma treatment

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.

Eyedrops
Glaucoma treatment often starts with medicated eyedrops. 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 eyedrop, make sure to ask how long to wait between applications. 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 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 eyedrops 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 eyedrops. If you have an allergy or sensitivity to sulfa drugs, don’t use these medications unless there’s no alternative.
  • Prostaglandin-like compounds. These eyedrops 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 eyedrops 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 eyedrop, 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 eyedrops 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 .This procedure is done in a hospital or an outpatient surgery center. You’ll receive eyedrops, 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 eyedrops 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 eyedrops 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.

Lifestyle

If you have elevated intraocular pressure or glaucoma, follow these lifestyle tips.

Sip fluids frequently. Drink small amounts of fluids over the course of a day. Drinking a quart or more of any liquid within a short time may temporarily increase eye pressure.
Exercise safely. Regular exercise may reduce eye pressure in open-angle glaucoma. However, eye pressure may increase after exercise in one form of secondary glaucoma — pigmentary glaucoma, an inherited disorder marked by dispersion of pigment granules throughout the eye. With vigorous exercise, the pigment granules can become stirred up and deposit themselves on the trabecular meshwork causing an increases in pressure. It’s especially important to avoid head-down yoga positions and stretches, since these positions may increase intraocular pressure. Talk to your doctor about an appropriate exercise program.

Glaucoma Prevention

Get regular eye care. Regular checkups can help detect glaucoma in its early stages before irreversible damage occurs. As a general rule, have eye exams every two years if you’re between the ages of 18 and 60, and every year if you’re older than 60. If you have one or more risk factors, you should have eye exams every one to two years until you’re 60, and every year after that.
Treat elevated eye pressure. A large trial at the National Eye Institute found that glaucoma eyedrops could reduce eye pressure by an average of 22 percent. In the same trial, daily use of eyedrops reduced the risk that elevated eye pressure would progress to glaucoma by nearly 50 percent in African-American study participants.
Control your weight and blood pressure. Recent studies have shown that insulin resistance — which may result from hypertension and obesity — is linked to elevated intraocular pressure
Wear eye protection. Serious eye injuries can lead to glaucoma. Wear a mask or goggles when you use power tools, play high-speed racket sports on enclosed courts or otherwise risk being hit in the eye.