Read an Excerpt
What Your Doctor May Not Tell You About Glaucoma
By Gregory K. Harmon Nancy Intrator
Warner BooksCopyright © 2004 Gregory K. Harmon, M.D., and Nancy Intrator
All right reserved.
How much do you know about glaucoma? What are the warning signs? Who is at risk? How is it diagnosed? Can you start losing your sight without knowing it? Is there any way to stop glaucoma? Can glaucoma damage be reversed?
Are your answers to these questions based on myth or fact? The list of questions goes on and on. The price of not knowing the correct answers is high: Untreated, glaucoma can lead to blindness.
Most people can recite the warning signs of cancer. Just about everyone knows the risk factors for heart disease. But how many people know the facts about glaucoma?
Ask a fifty-year-old man about glaucoma and he might reply, "Only old people get glaucoma. I am young, and I have perfect vision. I don't need to worry about that." (Myth!) A person who believes that myth could go years without getting an eye exam. Now, imagine that this same man is age fifty, black, and diabetic. Since blacks tend to develop glaucoma earlier and more often, this man now has three serious risk factors for the disease-his age, race, and diabetes-and he doesn't even know it.
Here's another scenario: An elderly woman is diagnosed with glaucoma. She believes that glaucoma does not run in families. (Myth!) In this era of managed care, her doctor may simply not have enough time to sit down and explain that the disease is often hereditary and that other members of her family should be sure to have their eyes checked, regardless of their ages. Or maybe he will tell her, and she will just forget to pass along the message to her sons and daughters. Since her children are unlikely to know this fact about their own family history, they may be unknowing glaucoma victims for years, until a chance exam-or, worse, a deterioration in vision-reveals the diagnosis.
Or maybe you have been diagnosed with glaucoma, and although you have followed your doctor's instructions regarding medication meticulously, the pressure in your eyes just isn't coming down or your vision is worsening. You wonder if there is anything more you can do without resorting to surgery. So you sign on to an online chat group for glaucoma patients. Someone tells you that jogging can reduce eye pressure. (Not a myth!) Another warns that wearing tight neckties can increase eye pressure and glaucoma risk. Really? (Not a myth!)
Since glaucoma is the leading cause of preventable blindness, we should all know the facts about this "sneak thief of sight." The first step is in knowing what not to believe. Learn how to separate myth from fact.
THE MOST COMMON GLAUCOMA MYTHS
Myth 1: All people with glaucoma have elevated intraocular pressure (IOP).
Many people believe that glaucoma is a disease characterized and defined by elevated IOP. Actually, elevated IOP is a risk factor for glaucoma and is not the disease itself. The common thread among all glaucoma is damage to the optic nerve rather than elevated IOP.
There are more than forty different types of glaucoma, and not all of them are associated with elevated IOP. Glaucoma specialists believe that some forms of glaucoma are strongly related to vascular changes and impaired "nutrition" (poor blood flow) to the optic nerve.
Myth 2: Only old people get glaucoma.
Though its frequency increases with age, glaucoma can strike at any time in a person's life. In fact, glaucoma diagnosed in an adult may be a result of elevated intraocular pressure that began when that person was in his or her teens. Approximately 1 in 10,000 babies is born with glaucoma, either because of a defect in the development of the drainage system of the eye or because of a congenital disease such as Marfan syndrome. Children between the ages of four and ten may develop a form of the disease called late congenital glaucoma, and for those affected between ten and thirty-five, the most common causes are hereditary disorders.
Individuals in certain high-risk categories may be more apt to become affected by glaucoma earlier in life. For instance, African Americans, who are six times as likely to suffer from glaucoma as Caucasian Americans, may begin to develop the disease in their forties (or younger).
Myth 3: Glaucoma is always inherited.
Family history is a strong risk factor for glaucoma, but an absence of family history does not mean a person is risk-free. An individual's risk for glaucoma is increased by any and all of the following factors: elevated intraocular pressure; age over forty-five; Asian or African descent; diabetes; nearsightedness; high blood pressure; significant eye injury; and/or long-term use of cortisone or steroids. However, if there is a family history of glaucoma, everyone in the family- from children on up-should be sure to get regular eye exams.
Myth 4: If you don't have high blood pressure, you cannot have high eye pressure.
Blood pressure and eye pressure vary independently. Controlling blood pressure does not mean IOP is controlled. However, high blood pressure is often-but not always- associated with elevated intraocular pressure. Interestingly, low blood pressure is strongly associated with some forms of glaucoma, such as normal-tension glaucoma (NTG).
Myth 5: You can tell if you are developing glaucoma because your vision will deteriorate or blur.
Most forms of glaucoma have no symptoms or cause no change in vision until late in the course of the disease. Once vision has been lost due to glaucoma, permanent damage has already been done to the optic nerve, and sight cannot be regained. That is why early detection and treatment before vision loss occurs is so vital.
Myth 6: You can test your own peripheral vision to see if you have glaucoma.
Most forms of glaucoma affect peripheral (to-the-side) vision rather than central (straight-ahead) vision. Many patients think that they can check their own peripheral vision by covering one eye, looking straight ahead with the other, and then checking to see what they notice at the side of their field of vision. On the basis of that type of "test," they decide that their peripheral vision is excellent and they could not possibly have glaucoma. However, it is impossible to evaluate the state of your vision without a true visual field test. That type of test is conducted in the eye doctor's office. Furthermore, as you will learn in the next few chapters, visual field testing is just one of the three vital diagnostic tests for glaucoma. It is also important for the doctor to look at the optic nerve head (disc) and to measure the IOP.
Myth 7: Ethnicity has nothing to do with glaucoma risk.
Blacks and Asians are at particularly high risk for developing glaucoma. Researchers have also recently discovered that glaucoma is far more common among U.S. Hispanics than originally thought. Unfortunately, U.S. Hispanics have been found to be less aware of their increased glaucoma risk than are members of other ethnic populations, such as blacks.
Glaucoma also manifests itself differently in various ethnic groups. For instance, on average, blacks develop glaucoma ten years earlier than Caucasians. According to statistics from The Glaucoma Foundation, blacks who are between forty-five and sixty-five years of age and have glaucoma are fourteen to seventeen times more likely to go blind than their Caucasian counterparts. Furthermore, glaucoma is the leading cause of blindness among blacks.
Myth 8: Nutrition and lifestyle have no effect on glaucoma.
Other than taking their medication and going for eye checkups as directed, patients once believed that there wasn't much they could do to manage their own eye health. We now know this is not true. Nutrition, exercise, stress management, and other aspects of your lifestyle can affect every part of your body, and your eyes are no exception. Here are just a few of the latest findings:
Research from the National Eye Institute (NEI) of the National Institutes of Health (NIH) has shown that the use of certain vitamin and mineral supplements can help preserve the health of certain structures within the eye. We have reason to believe that these substances may also help preserve the integrity of the optic nerve in glaucoma.
Aerobic exercise such as jogging, swimming, brisk walking, or bicycling can help reduce IOP by as much as 20 percent if performed for at least thirty minutes, at least three times per week. Glaucoma patients should take care to avoid activities like scuba diving and yoga positions that involve standing on the head, since they can raise IOP.
Smoking is associated with elevated IOP. Stop smoking.
Myth 9: It is painful and time consuming to be tested for glaucoma.
Nothing could be farther from the truth. There are three basic tests for glaucoma:
1. The ophthalmoscopic exam, in which the doctor looks into the eye and views the optic nerve.
2. Tonometry, in which a small instrument touches the front surface of the eye and measures the eye's pressure.
3. The visual field test, in which the eye is shown flashes of light that the patient is asked to detect in order to determine whether any side vision has been lost.
These tests are painless and relatively quick to administer.
Myth 10: Your intraocular pressure is the same day and night.
Actually, IOP varies throughout the entire twenty-four-hour period, and these variations are more important than we previously thought. Patients with greater-than-normal variations in diurnal and nocturnal (daytime and nighttime) IOP are more likely to have progression of their glaucoma.
Myth 11: Smoking marijuana is a good way to treat glaucoma.
For some people it might sound too good to be true: getting high under doctor's orders. It is true that clinical studies have shown that marijuana can lower intraocular pressure in individuals both with and without glaucoma. But does this mean smoking pot is an accepted and effective means of controlling glaucoma? The answer is a definite no.
The NEI initiated a number of clinical studies to determine the feasibility of marijuana as a form of glaucoma treatment. None of the studies showed the drug to be any more effective in lowering intraocular pressure than the Food and Drug Administration (FDA)-approved medications on the market. Furthermore, the active ingredient in marijuana has been shown to reduce blood flow to the eye. This reduced blood flow leads to a decrease in IOP. We now understand that adequate blood flow to the optic nerve is a critical factor in maintaining optic nerve health. Thus, the harmful effect of reducing blood flow to the eye negates the beneficial effect of lowering the IOP. In addition, studies showed that smoking marijuana could result in some potentially harmful effects such as increased heart rate and decreased blood pressure.
Myth 12: If one medication does not lower my IOP, my doctor will add a second one and then a third until my IOP is controlled.
Today there exists a large selection of safe and effective glaucoma medications. If the first one your doctor tries does not lower your IOP to the target level that has been chosen for you within a specified period of time, your doctor may switch you to a different medication rather than adding a second one to your regimen. It is much easier-and usually less expensive-for a patient to take one medication (monotherapy) rather than multiple medications, with a reduced chance of side effects. An easier treatment regimen enhances patient compliance. In glaucoma treatment, compliance is key!
Myth 13: The target IOP should be the same for everyone.
There is no one specific number that has been found to be the level at which a person's eye is safe from glaucoma-related damage. Some people require an IOP between 8 and 10 mm Hg while others can tolerate IOPs above 21 mm Hg. (Some basics: IOP is measured in millimeters of mercury. The abbreviation used is mm Hg. The normal range for IOP is considered 10-21 mm Hg.) Your doctor must be the one to choose your unique IOP target level.
Myth 14: Glaucoma always leads to blindness.
This statement is one of the most dangerous of all the glaucoma myths. According to The Glaucoma Foundation, 90 percent of all glaucoma-related blindness could have been prevented with proper treatment. In fact, glaucoma is the leading cause of preventable blindness. But you can't get treatment unless you know you have a problem, and currently only about half of all the people who have glaucoma are aware of it. If everyone had regular eye screenings and all glaucoma patients were diagnosed in a timely fashion, got the appropriate treatment advice, and followed all the doctor's instructions regarding medication, lifestyle changes, and-if necessary-surgery, there is a good chance that the sneak thief of sight could be stopped and blindness avoided.
Myth 15: If I have a cataract and glaucoma, I will need two separate surgeries.
There are times when patients who need both cataract and glaucoma surgery will require two separate surgeries, but this is not always the case. If a glaucoma patient is in need of cataract surgery, the doctor has three options: cataract surgery alone; staged surgeries (surgeries for the two conditions performed at different times); and combined cataract-glaucoma surgery.
Myth 16: When it comes to glaucoma treatment, there is nothing new to offer.
There is never a good time to be a glaucoma patient, but for individuals who do develop glaucoma, there has never been a time to be more optimistic. There is hope ... and lots of it! We now have an entirely new class of drugs that makes treating glaucoma safer, easier, and more effective than ever before: the hypotensive lipids. New surgical techniques have been developed for improving drainage and lowering pressure within the eye. It is only recently that we have learned of the role nutrition and exercise can play in controlling IOP.
Furthermore, only recently have researchers identified a new, potentially crucial risk factor for glaucoma: thin central corneal thickness (CCT). The discovery of this risk factor is already helping doctors identify patients at high risk for developing glaucoma. It is also helping doctors better understand and treat glaucoma in certain existing patients.
The future holds even more promise. Researchers have already identified a genetic marker for glaucoma. This could revolutionize screening and treatment techniques, possibly even preventing the onset of glaucoma in at-risk individuals. New methods of protecting the optic nerve (and thus preserving sight) in glaucoma patients are being developed. Researchers are experimenting with ways of suppressing an enzyme that produces retinal damage in glaucoma. Scientists are investigating the possibility of using stem cell technology to replace retinal cells that have been destroyed by glaucoma-related damage.
Excerpted from What Your Doctor May Not Tell You About Glaucoma by Gregory K. Harmon Nancy Intrator Copyright © 2004 by Gregory K. Harmon, M.D., and Nancy Intrator. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.