The Aging Eyeby Harvard Medical School, Sandra Gordon
DO YOU FIND IT DIFFICULT TO DISTINGUISH
BETWEEN BLACK AND DARK BLUE?
DO YOU WORRY EXCESSIVELY ABOUT GLARE
WHEN DRIVING AT NIGHT?
One out of every five of us is affected by impaired vision by the time we turn sixty-five. To help you preserve your vision now -- and beyond -- The Aging Eye discusses three common eye
DO YOU HAVE TROUBLE READING MENUS?
DO YOU FIND IT DIFFICULT TO DISTINGUISH
BETWEEN BLACK AND DARK BLUE?
DO YOU WORRY EXCESSIVELY ABOUT GLARE
WHEN DRIVING AT NIGHT?
One out of every five of us is affected by impaired vision by the time we turn sixty-five. To help you preserve your vision now -- and beyond -- The Aging Eye discusses three common eye disorders that pose the greatest threat to your vision: cataracts, glaucoma, and age-related macular degeneration (AMD). This valuable guide will help you determine whether you are at risk of developing these disorders, describes their symptoms, and discusses diagnosis and the latest treatments.
You will learn:
• What to expect after cataract surgery
• How glaucoma often progresses in the early stages without symptoms
• Whether you may be suffering from dry or wet AMD
• If laser surgery is right for you
• How to deal with presbyopia, dry eye syndrome, floaters and flashes, and retinal detachment
Finally, practical suggestions will inform you what you can do now to preserve your vision, from fine-tuning your diet and stopping smoking to wearing sunglasses and protecting your eyes from the ravages of diabetes.
A valuable user-friendly guide for everyone over fifty, The Aging Eye will give you the knowledge you need to safeguard your sight.
- Free Press
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- 8.30(w) x 5.50(h) x 0.40(d)
Read an Excerpt
Chapter 5: Glaucoma: The Stealth Sight Stealer
Like a thief in the night, glaucoma can snatch sight silently. Nearly four million people in the United States have a chronic form of the disorder, but at least half of those who have glaucoma don't know they have it. Like cataracts, glaucoma is usually painless, and progresses in the initial stages without symptoms. The National Glaucoma Research Foundation estimates that about 50 million people worldwide suffer from impaired vision and/or blindness from the disorder. Glaucoma is actually a group of diseases characterized by excessive fluid pressure in the eye, which can damage the optic nerve a bundle of more than one million nerve fibers that connects the retina, the light-sensitive layer of tissue at the back of the eye, with the brain. Good vision depends on a healthy optic nerve. In many cases, by the time vision loss from glaucoma is apparent, cells in the optic nerve have already been irreparably damaged and vision is gone forever.
Glaucoma is a major cause of blindness, and threatens two percent of the population over age forty, and becomes even more common with age. However, if glaucoma is caught and treated early through regular routine ophthalmology checkups, vision can almost always be spared.
Types of Glaucoma
Although twenty-five to thirty types of glaucoma exist, those described here are the most common.
Chronic Open-Angle Glaucoma
Chronic open-angle glaucoma, also called chronic glaucoma, accounts for more than 90 percent of all glaucoma cases. According to the National Eye Institute, glaucoma affects about 3 million Americans; it's estimated that half of those afflicted with glaucoma don't know they have it, due to the lack of early symptoms. Glaucoma strikes African-Americans most frequently. Most prevalent in people over sixty, glaucoma also tends to run in families.
According to the National Eye Institute, roughly 120,000 Americans are blind from this particular chronic form of the disorder. The name chronic open-angle glaucoma comes from the fact that the angle in the anterior (front) chamber of the eye remains open. For some reason that researchers don't fully understand, the aqueous humor the fluid in that front chamber drains too slowly. This leads to fluid backup and a gradual but persistent elevation in eye pressure, which can ultimately damage the optic nerve and cause vision loss if not caught in time and controlled by medication.
More specifically, the aqueous humor circulates through the pupil into the front compartment of the eye, nourishing the lens and lining cells of the cornea, the clear outer covering of the eye. The aqueous humor then drains out of the eye through Schlemm's canal via the circular trabecular meshwork, a sievelike drainage system of porous tissue, before being reabsorbed into surrounding blood vessels. As more aqueous humor is produced, excess fluid is eliminated through the trabecular meshwork to keep a healthy balance of pressure in the eye. The process works continuously as part of normal vision.
In open-angle glaucoma, the drainage system breaks down, and the outgoing fluid flows too slowly through the meshwork, or not at all. Consequently, the fluid can't leave the eye as it should, and backs up like water in a clogged sink. As a result, the internal pressure in the eye rises. This, in turn, puts stress on the optic nerve, which is responsible for transmitting visual signals to the brain, which then translate into images. If the pressure continues, the nerve fibers that carry the optical messages die, and vision starts to fade. Nerve fibers on the outer edge are affected first, which is why those with glaucoma typically develop blind areas at the edges of their field of vision. If left untreated, your peripheral vision gradually closes in, until the cells supplying central vision are killed off. Loss of vision may also result when the tiny blood vessels that feed the retina and optic nerve cannot deliver the blood into the eye because of the elevated pressure.
Acute Closed-Angle Glaucoma
A less-common form of glaucoma, which primarily affects farsighted individuals in their thirties and over, closed-angle glaucoma, also called acute glaucoma or acute-angle-closure glaucoma, is caused by a rapid increase in intraocular pressure. In acute closed-angle glaucoma, the pressure in the eye rises rapidly if the angle between the iris and cornea is narrow enough to allow the peripheral iris to block the drainage system, the trabecular meshwork. Anything that causes the pupil to dilate, such as dim lighting, some medications, and even dilating eye drops given before an eye exam, can cause the iris to block fluid drainage in some people. When this form of the disorder occurs, the eyeball quickly hardens, and the sudden pressure causes pain and blurred vision.
According to the National Eye Institute, glaucoma accounts for 4.5 million visits to physicians each year.
Low-tension glaucoma involves optic-nerve damage typical of glaucoma, but at normal eye pressures. The diagnosis is nearly always made after there has been some vision damage, because there are no early symptoms and no way to test for it. After other possible causes of the optic nerve damage and visual loss have been eliminated, lowering the normal pressure even further by medication and/or surgery will usually stabilize the condition.
This is a rare condition, present at birth and often inherited. It's attributed to a structural defect in the drainage angle, and is frequently found in both eyes. Congenital glaucoma usually responds to early surgery, and sometimes to medication.
Secondary glaucoma may develop as a result of some other eye problem, such as chronic inflammation, eye injury, advanced cataract, certain eye tumors, or as a complication of another medical illness, such as diabetes or lupus, vascular occlusion (blockage) in the eye, or even because of the use of systemic medication, such as prednisone or other similar medications.
Symptoms of Glaucoma: Open Angle
Unfortunately, chronic open-angle glaucoma the kind in which pressure gradually rises in the eye is insidious and may advance with few or no symptoms. You won't feel the increasing pressure in your eye, and may not notice blind spots and diminishing peripheral vision until late in the disease. Unfortunately, it's at this point that most people seek treatment. Occasionally, sufferers may be alerted that something is awry when they repeatedly need new eyeglass prescriptions, or have trouble adjusting to the dark. However, these symptoms generally occur in advanced stages of the disease; because the chronic form of this irreversible disease may not announce itself until it has done considerable harm, it's crucial to have regular eye exams and routine testing for glaucoma. Left untreated, glaucoma can lead to limited tunnel vision and eventual blindness.
Symptoms of Glaucoma: Closed Angle
Initial symptoms of closed-angle glaucoma, which may only last a few hours before a full-blown attack occurs, include severe pain, nausea, colored halos around lights, eye redness, and blurry or slightly decreased vision. Then, there may be rapid vision loss and throbbing pain in the eye. This type of glaucoma, which usually affects only one eye, can progress slowly or suddenly without symptoms.
If you see or feel any symptoms of closed-angle glaucoma, contact your eye doctor immediately. Closed-angle glaucoma is a medical emergency, because optic nerve damage and irreparable vision loss can happen within hours.
In general, to protect yourself from glaucoma, make an effort to have your eyes examined every two to four years by an optometrist or ophthalmologist if you're between age forty and sixty-four, and every one to two years by an ophthalmologist after age sixty-five. Be especially diligent if you have any of the risk factors mentioned for glaucoma, such as diabetes, a family history of glaucoma, or if you've had an eye injury earlier in life. Don't wait until your vision blurs or you experience other symptoms.
If you're diagnosed with glaucoma, you will need to see the eye docotor as often as four times a year to monitor the effectiveness of treatment, and to be sure the glaucoma is stable. Visual loss and blindness from glaucoma can be prevented if the disease is discovered before the optic nerve is severely damaged.
What Causes Glaucoma?
Although increased pressure within the eye, which ultimately damages the optic nerve, is the primary cause of glaucoma, that's not always the case. Some people who have normal intraocular pressure develop optic-nerve damage and vision loss, a condition referred to as normal or low-tension glaucoma. Similarly, some people with elevated intraocular pressure, a condition often called ocular hypertension, never develop glaucoma and visual loss. (These rare cases are best monitored closely by an ophthalmologist.) Clearly, there are other factors at play besides ocular pressure that cause glaucoma; research is underway to discover underlying causes of the disease.
In any event, if you have glaucoma and don't receive prompt and effective treatment, your vision will gradually deteriorate from the edges inward, until you can no longer see in your central line of sight and blindness develops. The damage that occurs in glaucoma is irreversible.
Who Gets Glaucoma?
No one is immune to glaucoma, but some people are more likely to develop the disease than others. The Baltimore Eye Survey, supported by the National Eye Institute, found that, by age seventy, about one in fifty Caucasions has glaucoma. In African-Americans, the problem is more severe, as by age seventy, one in eight has the disease. In general, you're at increased risk for glaucoma if you:
- are older than age forty
- are of African-American descent
- have a family history of the disease
- have elevated intraocular pressure (internal eye pressure)
- have had a past serious eye injury
Diabetes, severe nearsightedness, or farsightedness, routine use of steroid drugs, a history of anemia and shock, and/or a Scandinavian, Irish, or Russian background, are also associated with increased risk of one or more types of glaucoma. Just why glaucoma seems to appear as people get older isn't clear but, like other bodily processes that wind down with age, the eye's drainage system also seems to become less efficient at doing its job.
Glaucoma and Obstructive Sleep Apnea
It's estimated that about half of all normal-tension glaucoma patients and one-third of all primary open-angle glaucoma patients suffer from obstructive sleep apnea (OSA), a disorder in which sleep is interrupted because air can't flow into or out of your nose or mouth, although you continue to make efforts to breathe. Besides glaucoma, OSA is associated with irregular heart beat, high blood pressure, heart attack, and stroke. Snorers are often suspected OSA sufferers, as are those who are overweight. Although research on the connection between OSA and glaucoma is not conclusive, if you have been diagnosed with OSA, it's especially important to see your ophthalmologist regularly to be tested for glaucoma.
Glaucoma: What to Watch for
With open-angle glaucoma, you may not experience any symptoms, which is why it's important to see your eye doctor regularly for routine eye exams. If you notice any of the symptoms listed below, see your eye doctor immediately:
- difficulty focusing on close work
- loss of peripheral (side) vision
- not being able to adjust to a darkened room
- multicolored rings or halos around lights
- the need to change eyewear prescriptions frequently
In the closed-angle form of glaucoma, symptoms are much more defined. They include:
- blurred vision
- considerable eye pain
- rainbow haloes around lights
- sensitivity to light
- nausea (only when associated with the visual symptoms)
- vomiting (only when associated with the visual symptoms)
Closed-angle glaucoma is a serious condition and can cause blindness in a relatively short time, sometimes within hours. Don't wait to seek treatment. If you experience any symptoms, see your ophthalmologist immediately.
To test for glaucoma, the ophthalmologist evaluates fluid pressure in the eye through tonometry by measuring the force necessary to indent the eye. With the air-puff technique, a stream of air is blown gently against the eye. A more accurate measuring device, called an applanation tonometer, is placed on or near the eye, which has been anesthetized, to gauge the eye's resistance. Normal pressure is considered to be in the range of 12 to 21 millimeters of mercury (mm Hg) but, as mentioned earlier, people whose intraocular (internal eye) pressure falls in this range may still develop the disease. Likewise, those who have slightly elevated pressure may not be destined to get glaucoma: How much stress the optic nerve can withstand differs for each person and each eye. To confirm the presence of the elevated pressure, the doctor may repeat the tonometry test, as the fluid pressure in the eye may vary at different times of day.
A thorough evaluation of the optic nerve is necessary, and should be done as part of a routine eye exam. It's best done with a dilated pupil, which allows the doctor to better see the back of your eye to examine the optic nerve. The doctor uses both a slit lamp and an ophthalmoscope to look for any deterioration of the optic nerve. If the optic disk, the front surface of the optic nerve, is affected by glaucoma, a condition known as cupping may be observed. That is, the optic disk may appear indented, and its color normally pinkish yellow may turn pale and more yellow, because the advancing disease has hindered blood flow to the area.
If your doctor suspects glaucoma, he may perform an examination called gonioscopy, which examines the eye's drainage angle the area between the iris and the cornea for blockage. This procedure involves placing a special contact lens on the surface of an anesthetized eye. The lens has special mirrors and facets that, when studied through a slit lamp, give a detailed view of the corner of the eye and show whether the drainage angle is open, narrowed, or closed.
Fundus photography, which may be used to produce three-dimensional pictures of the optic disk the front surface of the optic nerve will provide a baseline for later comparisons of the disk. A change in the appearance of the optic disk in patients with glaucoma usually means that pressure hasn't been controlled, and an increase in therapy is needed. An ophthalmologist also may use laser polarimetry, a technique that uses a beam of laser light to measure and follow the thickness of the retinal nerve fiber layer just before they come together to form the optic nerve that carries the light to the brain.
Once you've been diagnosed with glaucoma, your eye doctor may also perform more general tests to determine the extent of your vision loss, if any. Each year, glaucoma patients typically undergo two to four examinations that involve measuring visual acuity, the optic disk, and the pressure in the eye. The doctor will also check peripheral vision to find out if there is lost side vision, and may perform other tests done at selected intervals to establish the stability of the disease or to note deterioration.
Medications for Glaucoma
Most types of glaucoma, including chronic open-angle glaucoma, can't be cured. Unfortunately, vision lost to the damage of glaucoma can't be regained. (It is best to detect and treat the glaucoma before any visual loss has occurred.) However, glaucoma can be controlled to keep the disease from doing further damage. The goal of therapy a lifetime commitment for both the patient and the physician is to control eye pressure and stop the disease from progressing.
Open-angle glaucoma treatment usually begins with topical medications eye drops or sometimes ointments that patients apply one to several times a day to help fluid better drain through the trabecular meshwork or to decrease the eye's production of aqueous humor. Depending on the severity of the glaucoma, multiple drops and, sometimes, pills may be required. Unfortunately, glaucoma medications can be expensive and may cause side effects, such as headaches, lower pulse and blood pressure, fatigue, respiratory problems, allergic reactions, impotence, and even a change in eye color. Most ophthalmologists begin with the lowest effective dose to minimize potential side effects and the cost of the drops. If side effects occur, consult with your eye doctor for advice on alternative treatment.
Types of Medications
The following classes of drugs are listed in the order in which an ophthalmologist is most likely to prescribe them to treat glaucoma. However, the doctor will personalize treatment based on the individual characteristics of each patient. Depending on the severity of glaucoma and your medical history, for example, your physician may prescribe these drugs in a different order, or may use two or more of the drugs in combination. (See the Appendix for specific drugs.) The more commonly used medications tend to have fewer and less severe side effects than those less commonly prescribed.
Prostaglandins: This topical drug is commonly used because it requires only one application per day. It lowers internal eye pressure by removing aqueous humor through the uveal tissues, which includes the iris, ciliary body, and the choroid, the inner lining of the eye. Prostaglandins may cause allergic reactions, uveitis (inflammation) within the eye, blurred vision due to macular edema (swelling of the macula, the central area of the retina), headache, and fatigue. In addition, for some people, this medication has startling cosmetic effects that include causing lashes to grow longer and thicker and changing the iris color from blue or hazel to brown. An ophthalmologist may thus be less likely to prescribe this drug for someone with hazel or blue eyes.
Beta blockers: These topical eye drops, similar to beta blockers used to treat some types of heart disease, are commonly prescribed for glaucoma, and are used once or twice daily. Topical beta blockers lower pressure in the eye by reducing the amount of aqueous humor produced by the eye's ciliary body, which is just behind the iris. This class of medication is usually well tolerated with continued use, but has potentially serious side effects. In a small percentage of patients, when the drug enters their system, they may experience a slowing of the heart rate, a sense of mental and physical lethargy, a decrease in libido (in men; the effect on women's libido has not been researched), and/or a worsening of asthma. Patients with chronic lung disease may experience serious breathing problems. Topical beta blockers may be used by patients who are also taking the drug systemically (not topically) for heart disease, but it's important to notify both your ophthalmologist and physician that you're doing so. Topical side effects include allergy and eye irritation.
Alpha-2 agonists: This medication, used two to three times a day, lowers intraocular (internal eye) pressure by both decreasing production of aqueous humor and increasing the fluid outflow from the eye. It may cause allergic reactions, eye irritation, dry mouth, general fatigue, and other symptoms.
Carbonic anhydrase inhibitors (CAIs): This class of medication, which can be administered either orally or topically, decreases eye pressure by reducing the amount of aqueous humor produced in the eye, as do beta blockers. CAIs may cause prominent side effects, including numbness and tingling in the hands and feet, excessive urination, loss of appetite, drowsiness, lethargy, depression, anemia, and allergic reactions. The eyedrop form of CAIs may have fewer side effects than the pills, but even the drops can cause an allergic reaction, a bad taste in the mouth, and the other side effects that the pills cause. If you have been prescribed CAIs, it's a good idea to be aware of these potential side effects and to keep your eye doctor updated.
Miotics: Miotics, the oldest of the currently used medications for glaucoma, improve the drainage system capacity when applied as eye drops. Pilocarpine, carbachol, and echothiophate iodide, a stronger miotic, may produce blurred vision by decreasing the size of the pupil. This may be especially troublesome if you have cataracts. These medications may produce nearsightedness in young glaucoma patients, limit night vision, and cause chronic inflammation in the eye or even retinal detachment. One of the miotics may also cause cataracts. Side effects may also include diarrhea, sweating, and other symptoms. Miotics are used infrequently, because their side effects on vision are more common and troublesome than those of many of the other glaucoma medications.
Adrenergics: These drops contain either epinephrine or dipivefrin, which becomes epinephrine (otherwise known as adrenaline) when absorbed into the eye. Adrenergics decrease the secretion of aqueous humor and increase the eye's outflow via the trabeculum, the eye's meshlike drainage system. Epinephrine, which is naturally secreted by the adrenal glands, is the agent that causes the heart to beat fast and palpitations to occur when you're frightened or angry. When used in the eye to increase the eye's outflow of fluid, it may cause similar systemic effects, such as heart palpitations. Topical local symptoms within the eye include the dilation of the pupil, allergies, and redness (a common cosmetic side effect).
Hyperosmotic medication: In the case of acute glaucoma, hyperosmotic medication (which reduces pressure in the eye by pulling fluid from the eye into the internal eye blood vessels, then out of the eye with the normal blood flow of the general vascular system), may be taken orally or injected.
There's a growing list of alternative treatments for glaucoma, including herbs, such as bilberry extract, meditation, and biofeedback to lower intraocular pressure and improve blood flow to the eye. While these natural therapies are often based on sensible ideas about good health, there have been few controlled studies to support or discredit their effectiveness. In general, avoid using them in lieu of conventional treatment that has been proven based on numerous clinical studies. If you'd like to try a natural therapy, tell your eye doctor. Despite their questionable status, some doctors recommend them in conjunction with proven therapies.
Side Effects of Glaucoma Drugs
Although the symptoms and side effects from glaucoma medications appear formidable, in actual practice, most don't occur in the average patient. Most people tolerate these medications either alone or in combination to treat glaucoma. If you have problems with any medication, tell your eye doctor. You may be able to switch to a different dosage, or even to a new drug. Also, remember that glaucoma medications are potent drugs. If you're taking other medications for other conditions, even something as simple as a decongestant, be sure to tell your ophthalmologist and pharmacist, to avoid adverse drug interactions.
Some beta blockers used to treat glaucoma may lower levels of HDL ("good") cholesterol and increase the risk of heart disease, the nation's number-one killer. If you're taking beta blockers for glaucoma, be sure to tell your personal physician, particularly if you have heart disease or are at increased risk for the condition due to elevated cholesterol, your age, or other factors, such as a family history of heart disease.
Minimizing Side Effects
Although topical eyedrops help to control pressure in the eye, they may have accompanying side effects, such as dizziness or breathing trouble, which could limit or prohibit their continued use. These side effects may affect the eye itself, causing stinging, burning, or redness, or they may be systemic, as the drops enter the bloodstream after they're absorbed through the nose and throat. You can avoid absorbing too much of the medication into your system by turning your head outward when you apply your eyedrops. This tactic lets the excess liquid run to the outer reservoir of your eye instead of allowing it to pool in the inner corner, where it can be absorbed into the nose and throat. Another trick: After you apply your eyedrops, compress the tear duct leading into the nose, by placing your index finger deep within the inner corner of your eye; this allows more of the medicine to stay in your eye and prevents it from entering your nose and throat.
If eyedrops prove difficult for you, talk to your eye doctor about alternatives. You might be able to use gels or ointments. Another treatment option is to insert a medicated disk with a time-release mechanism in the lower conjunctiva sac (the clear membrane that covers the front portion of the white of your eye) between the lid and the eyeball. However, these drug delivery systems tend to be more expensive than traditional medications, and are often more cumbersome.
Not to be confused with over-the-counter eyedrops for common eye irritations, eyedrops for glaucoma are serious medicine. Here's a step-by-step guide to applying topical eyedrops, so you can routinely get the proper amount of medication into your eye.
1. Before applying your eyedrops, wash your hands.
2. To apply the medicine, bend your neck back so that you're looking up at the ceiling; turn your head slightly outward, and use one finger to pull down your lower eyelid to create a small pouch for the medicine.
3. Without letting the tip of the bottle touch your eye or eyelid, squeeze just one drop of the medicine into the space between your eye and your lower eyelid. If you squeeze more than one drop, you're probably wasting medicine, wasting money, and possibly getting too much medicine into your system.
4. After the drop has entered your eye, close your eye, then press a finger deep within the inner corner of your eye and hold for several minutes. Gently closing your eye will ensure the medicine spreads over its surface.
5. After you've put eyedrops in your eyes, wash your hands. While capping the medicine, try not to let the tip of the bottle touch anything, such as a table or countertop, to avoid contamination.
6. If you need to take more than one eye medicine, wait ten to fifteen minutes before applying any subsequent medicine, to allow each medicine to be absorbed into your eye. Different drops placed in the same eye too soon will each dilute the concentration of each medicine. Generally, the drops should be used every twelve hours if prescribed twice a day, every eight hours if prescribed three times a day, and so forth.
Sticking with Your Medication Routine
Because glaucoma has no symptoms, you may be tempted to stop taking your medication or forget to take it. However, to prevent glaucoma from doing further damage, it's important to use your eyedrops and/or take pills for glaucoma, as long as they help to control your eye pressure for as long as your doctor recommends. Even if the disease is stable and symptoms disappear, don't stop taking your medicine unless your doctor advises it.
Regular exams are equally important because, without an exam, it's not possible to tell whether fluid pressure in your eye is in a safe range, or if your visual field is slowly changing. Patients with chronic glaucoma are commonly examined two to four times a year to ensure that medication is effectively controlling eye pressure, and that their vision is being preserved. Work with your physicians and other caregivers to ensure that you can properly maintain your glaucoma therapy. If you have questions about your drugs, trouble following your treatment plans or difficulty applying the drops, mention them to your doctor, and ask for advice and solutions.
Glaucoma Surgery: When Drugs Don't Help
If the pressure in your eye can't be controlled with the maximum tolerated medication, your ophthalmologist may advise that you undergo laser or conventional glaucoma surgery. The ophthalmologist, who commonly deals with these issues, will doubtless have literature or web sites for you to consult, and will be prepared to discuss the reasons for performing the operation, as well as the risks and benefits of surgery. (For more information, you may wish to do your own research. "Resources," starting on page 229, is an excellent reference tool.) The following types of surgery for glaucoma are currently available.
Laser trabeculoplasty: When medications aren't totally effective, your doctor may recommend laser trabeculoplasty, a form of laser surgery that helps fluid drain out of the eye in open-angle glaucoma. Laser surgery can't reverse the damage that's been done, but it can prevent glaucoma from progressing, in many cases. The ophthalmologist usually performs the procedure in her clinic or office, using a high-energy laser beam to burn tiny spots onto the surface of the eye's trabecular meshwork, which is part of the eye's anterior chamber drainage system. The doctor makes about fifty burns in half of the trabecular circumference; the burns stretch the existing holes in the meshwork to allow fluid to flow out of the eye more freely.
Before the procedure, which is typically painless, the doctor numbs the eye with drops, which allow a special contact lens with mirrors to be placed on the eye. As you sit in a comfortable position at the slit lamp, the ophthalmologist applies the contact lens as your other eye fixes on a target. You may see flashes of green or red light as the laser is focused and fired. The treatment takes less than one-half hour. The doctor will check the internal eye pressure after treatment before allowing you to go home. The doctor will also prescribe drops for minor inflammation, along with the regular glaucoma medicines, and will schedule several followup visits to monitor your eye's intraocular pressure. You may experience blurred vision and sensitivity to light for a day or two after the operation, but you shouldn't feel any pain or discomfort.
While laser surgery is often helpful, the benefits may not be permanent: If it's only partially successful, your doctor may need to perform the procedure again on the other half of the trabecular circumference. Moreoever, some patients don't respond to laser surgery. After about two years, more than half of all patients experience a rise in eye pressure to unsafe levels and will require conventional surgery. Still, most ophthalmologists will recommend trying laser surgery first, because conventional surgery carries the additional risks of hemorrhage, infection, and other problems.
Laser iridotomy: Your eye doctor may suggest this technique, which is often effective in treating acute closed-angle glaucoma, even before prescribing medication. Using a laser, the surgeon creates a small opening in the outer edge of the iris to help the aqueous humor better drain from the back chamber to the front chamber. The ophthalmologist can create this opening without making an actual incision in the eye, an advance over the older, prelaser procedure, which required surgical incision and scissor excision of the iris. Laser iridotomy cures closed-angle glaucoma in many patients, making drug treatment unnecessary. Topical medication and/or conventional surgery may be warranted, however, if the eye has suffered permanent damage before the iridotomy is performed, such as the iris permanently adhering to the trabecular meshwork, blocking the flow of aqueous humor out of the eye.
Conventional incisional surgery: Conventional surgery is used by ophthalmologists when medications or laser surgery aren't successful in treating chronic open-angle glaucoma, or when acute closed-angle glaucoma has gone untreated and caused permanent damage. Conventional incisional surgery, also known as filtering surgery or trabeculectomy, creates a new drainage system when the trabecular meshwork is either scarred or no longer functions. It can be done as outpatient surgery.
In the most common procedure, the trabeculectomy, an eye surgeon opens a flap of tissue to form a new passageway, so that fluid can drain from the front chamber of the eye to a space created beneath the conjunctival tissue under the upper lid. This filtering bleb helps bring pressure in the eye down, and eye fluid is reabsorbed into the bloodstream.
In an alternative technique, used in scarred tissue, the surgeon implants a special plastic valve to provide drainage for outflowing eye fluid. Filtering surgery is successful in 80 to 90 percent of patients; the other 10 to 20 percent can usually undergo further surgery, which usually improves eye pressure adequately. Most patients can eliminate or reduce their use of glaucoma medication after filtering surgery. This type of surgery is an involved procedure, so ask your ophthalmologist to refer you to an eye surgeon who has the proper experience and expertise if your ophthalmologist doesn't do this type of surgery. The surgery isn't without risks or complications; filtering blebs may leak fluid and may be susceptible to infection. The surgery may also lead to blurred or decreased vision from retinal swelling at the macular of the retina, and can also cause the development of cataract.
Cyclodestructive surgery: In this procedure, the surgeon uses a cool laser or a thermal (heat) laser to treat glaucoma by destroying the cells in the eye's ciliary body (the vascular structure behind the iris whose surface cells produce aqueous humor). The surgeon applies a probe, usually on the surface of the eye, and treats the secreting cells of the ciliary body through the intact sclera (the white of the eye). This reduces the amount of aqueous humor formed in the eye. Cyclodestructive surgery is useful when other methods of glaucoma control haven't been successful.
If you're diagnosed with advanced glaucoma, your eye doctor will likely recommend a course of therapy to preserve and prolong your vision based on your unique patient characteristics, which may include your race. According to the National Eye Institute of the National Institutes of Health, African-American and white patients with advanced glaucoma may respond differently to surgical treatments for the disease. Research suggests that African-American patients with advanced glaucoma not responding well to medications benefit more from a surgical treatment regimen that begins with laser surgery, while Caucasians benefit more from one that begins with trabeculectomy (conventional incisional surgery). However, filtering surgery is usually successful for all patients.
Because early diagnosis and treatment remains the key to preserving sight, the surest way to prevent glaucoma-related blindness is to know the risks, and to have your eyes examined regularly. If you have risk factors for glaucoma, such as being over the age of sixty, having a history of glaucoma in your family, or a having had a past eye injury, your eye doctor is likely to monitor three things: intraocular (internal eye) pressure, your optic nerve, and the quality of your peripheral vision. If you've been diagnosed with glaucoma, your vision may be protected for a lifetime if your glaucoma is properly treated.
As you read this, research studies are underway to better diagnose, monitor, and treat glaucoma. In the past, such studies have led to new ways to diagnose and monitor glaucoma, as well as a variety of new drugs to reduce intraocular pressure, which, in turn, reduces pressure on the optic nerve. However, even those medications don't necessarily stop the disease from progressing. Many people still continue to have vision loss due to glaucoma, because there are mechanisms other than elevated intraocular pressure that lead to loss of vision.
A likely suspect is the untimely death of cells in the optic nerve. On the horizon may be a new type of drug for glaucoma that prevents the early death of nerve cells. This medication, which is already being used in Europe and the United States to treat patients with Parkinson's disease, diabetic neuropathy, and AIDS-related dementia all of which involve nerve cells that die in an untimely way may help keep optic nerve cells alive, thereby preserving vision. If you've been diagnosed with glaucoma, stay tuned. Government organizations, such as the National Eye Institute of the National Institutes of Health, and others, are working hard to develop new drugs and therapies that may treat glaucoma and thereby protect and improve visual health.
- Glaucoma is a major cause of blindness, and threatens 2 percent of the population over age forty, becoming even more common with aging. If glaucoma is caught in its early stages through routine vision checkups, vision can almost always be saved.
- Typically, those with glaucoma develop blind spots at the edges of their vision, which can gradually close in, eventually leading to blindness.
- Risk for glaucoma is increased for those who are older than age forty, have a family history of the disease, have elevated intraocular pressure, are of African-American descent, or have had a serious eye injury in the past. Those at risk should see an eye doctor yearly.
- Open-angle glaucoma, among the most common forms of the disease, gradually increases pressure within the eye, perhaps because the natural drainage system in the eye is clogged. The increased pressure stresses the optic nerve; if nerve fibers in the optic nerve die, vision will fade.
- A less common form of glaucoma, closed-angle glaucoma, is marked by a sudden increase in internal eye pressure, because fluid in the front chamber of the eye can't drain. Closed-angle glaucoma is a medical emergency because optic-nerve damage and irreparable vision loss can occur within hours.
- An eye doctor should be seen promptly if it becomes difficult to focus on close work; side vision disappears; and/or eyes lose their ability to adjust to a darkened room. All are potential signs of open-angle glaucoma. Other warning signs include blurry vision, considerable eye pain, rainbow haloes around lights, headaches, nausea, or vomiting. All may be signs of closed-angle glaucoma, a medical emergency.
- Being diagnosed with glaucoma doesn't mean future blindness. Medication and surgery is available to help prevent the disease from progressing to complete vision loss.
- Unfortunately, there's no way to prevent glaucoma other than knowing the risks and regular eye examinations.
Copyright © 2000, 2001 by the President and Fellows of Harvard College
Meet the Author
Harvard Medical School is a center of medical expertise comprised of dozens of affiliated hospitals, clinics, research foundations, and publication centers. Throughout its history, Harvard's doctors have made important medical breakthroughs, including the discovery of anesthesia, the first human organ transplantation (Nobel Prize), and the discovery of the polio virus (Nobel Prize).
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