Glaucoma—Insidious Stealer of Sight!
SHE is a bright, active woman in her early 60’s. She has worked happily in her kitchen for more than 20 years and knows every inch of it well.
But this day, as she works at the counter, she turns and bumps her head on an open cabinet door. She mutters to herself about the dangers of absentmindedness. Minutes later she trips over a pair of shoes left near the back door.
This is neither absentmindedness nor a sudden lack of coordination. It is an insidious thief—glaucoma—slowly stealing this woman’s sight! Left untreated, it will steal it all. But glaucoma can be stopped and even prevented. How?
Your Remarkable Eyes
To begin with, you need to understand something of the design of your eyes. Your eye is a ball of fibrous tissue filled with a clear fluid. The opaque white part of this ball is the sclera. Through the clear part, the cornea, you can see the delicate-looking tissue that gives your eyes their color—the iris. Light enters your eye through the pupil, that dark opening in the center of the iris.
Just behind your pupil is a clear lens. Tiny muscles change its shape to focus what you see onto a screen of light-sensitive cells at the back of your eye—the retina. To function, your eyes must be clear inside and inflated to hold their roundness.
Your eyes are not empty. The Creator has provided them with clear substances that are constantly self-replacing. Most of the eye—the rear part behind the lens—is filled with vitreous (glassy) humor, a clear, jellylike fluid. The front part of your eye, between the vitreous humor and the cornea, contains aqueous humor—a watery fluid, as its name suggests. Your iris divides this watery part of your eye into two compartments: the front, or anterior, chamber and the rear, or posterior, chamber.
Behind the iris, the ciliary body is constantly producing this watery fluid. The fluid stays under a slight pressure, which varies somewhat with the normal changes in your body. The fluid flows gradually through your pupil into the anterior chamber, then to the edge of your iris. From there it flows through a meshwork of tissue into a drainage canal.
But what if some condition blocks the pupil, the meshwork, or the canal? When inflow exceeds outflow, pressure begins to build. The aqueous humor presses against the vitreous humor. The vitreous humor, in turn, presses with increasing force on the blood vessels and photoreceptor cells of the retina.
Nerve fibers from these cells come together at the back of the eye to form the cup-shaped optic nerve head, usually referred to as the optic disk. Since there are no vision cells within this disk, you have a tiny blind spot there. As pressure builds, blood flow is restricted. This smooth, pink optic disk becomes pale and irregular. Its cupped center deepens and grows wider. Deprived of blood, vision cells lose their sensitivity and die. The blind spot grows, and the visual field shrinks. For years this irreversible damage slowly progresses.
Chronic open-angle glaucoma, caused by deteriorating fluid drainage, accounts for 70 to 95 percent of all glaucomas. Victims can still see and read well because the cells at the centers of their eyes are the last to be attacked. There are usually no symptoms at all in the early stages.
As chronic glaucoma stealthily progresses, some persons may complain vaguely of tired or watery eyes or feel that they need new glasses. Later on, they may notice a halo around lights and feel pain around their eyes. But for many, there is no warning until the loss of peripheral vision causes an unexplained “clumsiness.” Finally, even central vision becomes noticeably poorer. By then, glaucoma has stolen most of the victim’s sight.
Acute, or closed-angle, glaucoma accounts for about 10 percent of the cases reported in the United States. This is primarily an ailment of the elderly because our lenses enlarge with age, especially when cataracts are present. In eyes that have a shallow anterior chamber and a narrow angle between the cornea and the iris, the enlarged lenses gradually move forward to block the aqueous flow through the pupil. Pressure builds behind the iris. It bulges forward, squeezing shut the drainage meshwork that lies at the point of the angle and the canal.
Closed-angle glaucoma is usually not chronic but acute. Instead of a slow buildup of pressure, there is a sudden onset of increasing pain, sometimes accompanied by blurred vision, nausea, and vomiting. This is a true medical emergency! If the pressure is not relieved within 48 to 72 hours, there may be permanent damage to the trabecular (drainage) meshwork, and that will lead to irreparable damage to the optic nerve.
In other kinds of glaucoma, the trabecular meshwork may be blocked by inflammation, disease, or loose pigment from the iris. Trauma, such as a blow to the eye, can trigger glaucoma. Some children are born with congenital glaucoma and must be treated in infancy. Because they cannot see or read as well as others, they may even erroneously be thought to have learning disabilities.
Most Important—An Early Diagnosis
The good news about glaucoma is that most cases can be treated if they are diagnosed early. Regular eye examinations, especially for anyone over 40, are vital.
In one method for checking eye pressures, the doctor anesthetizes your eyes with drops, then gently presses an instrument called a tonometer against your cornea. The tonometer measures the pressure inside your eye by applying a gentle force to the cornea. This is the basic test for glaucoma. But it is not always enough to make sure that glaucoma is not present.
“I thought I had something in my eye,” said one middle-aged woman. “I was pulling out eyelashes because I thought they were irritating my eye. Then I began to feel tingling sensations in my scalp, and my eyes began to hurt.” She was examined by her family doctor, by an ophthalmologist who checked her eye pressure, and by a neurologist. They attributed the symptoms to a nervous condition.
She and her husband sought a second opinion from another ophthalmologist, who gave her a battery of tests. A provocative test—drinking a quart [1 L] of water at one sitting—forced her eye pressure high enough to reproduce her symptoms. She was diagnosed as having chronic closed-angle glaucoma. Her sight was saved.
Why did the first ophthalmologist fail to diagnose glaucoma? For one thing, eye pressure can vary throughout the day and the month. For another, some people can be suffering the effects of glaucoma even at normal pressures. Only a series of tests can definitely establish that glaucoma is not at work.
“There are three areas of major concern in diagnosing glaucoma,” says one eye surgeon. “They are eye pressure, the appearance of the optic nerve, and the visual field. If all three are abnormal, we then begin to ask, ‘What kind of glaucoma is it?’”
If glaucoma is diagnosed, the eye doctor may examine the rim of your iris and measure the depth of your anterior chambers. He will also ask questions about your general health, which greatly affects your eyes. High blood pressure is an example. “Anyone with a family history of glaucoma should have their eyes checked before treatment to lower their blood pressure,” says one doctor. The reason: High blood pressure raises eye pressures. The irritation of the eyes upsets the sufferer, and blood pressure and eye pressure race in a continuous cycle.
“One lady I know of was admitted to the hospital with a hypertensive [high blood pressure] crisis,” continues the doctor. “Her eyes were hurting, so an ophthalmologist was called. He treated her glaucoma quickly with laser surgery. Her eye pressure dropped immediately—and so did her blood pressure.” If the doctors had reduced her blood pressure first, she might have gone blind. The high fluid pressure in her eyes might have prevented the blood supply from reaching her optic nerves.
Advances in Treatment
All treatment for glaucoma aims at reducing the pressure inside the eyeball to halt damage to the optic nerve. Great strides in such treatment have been made in recent years. For open-angle glaucoma, the treatment is often the daily use of eye drops. Oral drugs may also be prescribed to reduce the production of aqueous fluid or to increase its outflow. Surgery is sometimes called for. A type of laser treatment, an outpatient procedure, improves drainage dramatically, reducing pressure by up to 25 percent in most cases.
For closed-angle glaucoma, medication provides temporary relief. The pressure can usually be relieved permanently by iridotomies—openings in the iris. Today, they can be made in just a few minutes. The eye surgeon anesthetizes each eye with drops, then makes small but visible perforations in the iris with a laser. Often the surgeon can observe the fluid rushing through the first opening he makes.
Special surgical techniques have been developed to treat rarer forms of glaucoma. In neovascular glaucoma, an excess of blood vessels blocks the drainage meshwork. The eye surgeon may use a laser to destroy part of the fluid-producing tissue or may implant tiny tubes that let fluid bypass the meshwork. He can also use ultrasound, cryosurgery (freezing), or laser methods to disturb the edge of the retina. Blood flow to that area will increase, so that the blocking blood vessels will shrink. Only a small percentage of glaucoma cases remain untreatable.
How You Can Protect Your Sight
Preventive care is vital. Have your eyes examined every two years. If you are over 40 and have any risk factor in your background, including diabetes, cataracts, eye inflammation, extreme nearsightedness, coronary artery disease, or a family history of glaucoma, have an examination at least once a year.
Do not treat symptoms lightly. See an eye doctor immediately.
Seek a second opinion if you are in doubt. Ask friends about eye doctors they know and whether these doctors have a variety of up-to-date equipment. Were their examinations thorough?
Have you been diagnosed as having glaucoma? Follow your doctor’s recommendations closely. One medical journal states that lack of compliance by the patient is the number one cause of failure to control glaucoma.
Never miss an appointment. Most doctors schedule checkups for glaucoma patients every three to six months because their eyes can undergo major changes in that time. Also, most people develop a tolerance to their eye drops after a year or so and often need a new prescription.
Be faithful about taking your medication. Do not use it past the expiry date. Be sure to let other doctors treating you know about your medication, especially if you have heart problems. Carry a card that states you have glaucoma and that gives your eye doctor’s name, the name of your medication, and the dosage.
Remember: Glaucoma can almost always be defeated—if we know what to do about it and are diligent about protecting ourselves.
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Optometrist testing for glaucoma