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This should introduce you to the basic concepts of open-angle glaucoma and its therapy. It is intended to increase your basic knowledge, allowing you to ask more questions that are specifically related to your type of glaucoma and where you are in the spectrum of the disease.
Medicine is an art and not a science. Although the treatment of glaucoma is based on many years of scientific investigations and upon a large volume of research, the treatment of glaucoma involves a great amount of diagnostic skill. It is difficult, for both the physician and patient, to treat a disease that has no symptoms until it produces blindness. Therapies for glaucoma involve long-term goals. These goals involve preserving the most amount of vision possible. A patient should realize, from the beginning, that it is impossible to return any vision lost from glaucoma. However, a patient most likely can keep most of vision he currently has.
Communication between the doctor and patient is paramount in the treatment of glaucoma. One of the best ways of combating blindness may be for you and our doctors to work together as a team. Our doctors believe that it is important for you to know as much about glaucoma as possible, so that you can ask the questions that are important to you. In fact, our doctors encourage you to ask these questions. They feel that the more you know, the more likely you are to be a better patient and comply with your therapy. The more you comply with your therapy, the better you are able to preserve your vision.
OPEN ANGLE GLAUCOMA
Open-angle glaucoma is one of many forms of glaucoma. Open-angle glaucoma, unlike other diseases, usually has no symptoms. Most forms of open-angle glaucoma have an eye pressure which is too high for a person’s eye. Glaucoma causes vision loss and blindness if left untreated. The visual loss begins in the side vision and is not noticed. It progresses slowly, so that it is usually impossible to detect changes in side vision until they are large and dangerous. Our goal is to treat the eye pressure in hopes of permanently maintaining your vision similar to the vision that you had when you were first diagnosed.
Glaucoma should NOT BE CONFUSED WITH either cataract or macular degeneration. All three diseases are more common in elderly populations. The blindness caused by cataract can be reversed with surgery. It is uncommon to regain vision lost from macular degeneration.
UNDERSTANDING EYE PRESSURE
The eyeball is like a basketball or a tire, and in this way it has a pressure. Fluid (called aqueous humor) is made inside the back portion of the eye called the "ciliary body". This fluid is created inside the eye, and nourishes the eye. It slowly travels from the back part of the eye to the front of the eye to an area called "the angle" or "trabecular meshwork", where it then exits the eye.
Elevation of your eye's pressure is never caused by too much fluid being made. The elevation in your eye's pressure is caused by blockage to the drainage area of your eye (the angle or trabecular meshwork).
Glaucoma can cause blindness if left untreated. Lowering the pressure in the eye, either by using eye drops, laser surgery, or actual incisional surgery can prevent the progression of glaucoma, thus sparing vision.
If our doctors determine that the pressure in your eye should be lowered, they will first determine what an appropriate goal, or target pressure should be. Following that they will use therapies that do one of the following:
- Decrease the amount of fluid which is made. (This is similar to turning off a faucet of a sink which may be overflowing).
- Increasing the amount of fluid which the drainage system allows to leave the eye (this is similar to using Liquid Plumber®).
The pressure always changes and can vary quite a bit, especially in glaucoma patients. This is neither abnormal nor surprising. One can imagine that the "thermostat" within the eye which sets and regulates the eye's pressure does not work as well in eyes with glaucoma. A single pressure reading can be deceiving or misleading. The doctor might therefore place more emphasis on evaluations of the optic nerve appearance and how the eye functions when performing a visual field than one specific eye pressure reading.
There is no known relationship between eye pressure and stress or tension. Eye pressure is not related to caffeine use. Eye pressure and blood pressure are NOT related. The only exceptions to this are as follows:
- In younger individuals, it may be less likely for a person to have both glaucoma and high blood pressure.
- However, in older individuals, it may be more likely for people to have both high blood pressure and glaucoma.
- Some medications which lower your blood pressure may also lower your eye pressure.
To measure eye pressure, an eye drop, which might sting for a few seconds, is placed on your eye. This numbs your eye. A probe is next placed on your eye which measures the pressure inside of it. The pressure inside your eye is related to how much force is needed to indent your cornea just a little bit. This process does not hurt and only takes a matter of seconds!
There is no such thing as a “normal” eye pressure. Each person and each eye has a unique threshold above which damage to the optic nerve develops. Therefore we have to develop an individualized treatment plan for each patient. Your ideal pressure may be higher or lower than your neighbors.
TESTING FOR GLAUCOMA
The optic nerve is the part of the eye which is most affected in glaucoma. The optic nerve is not a "single" nerve, but a collection of approximately 1,000,000 (one million) nerve fibers. Normally, every human loses 500 fibers a year through normal aging. It is the only living nerve in the human body which can be seen without making an incision. The optic nerve is similar in many ways to the film in a camera. The optic nerve is the structure that sees images and tells the brain what the eyes are seeing. When glaucoma injures these nerve fibers, eventually killing some of them, it causes loss of vision. When the doctors detect nerve damage, this early damage is the first stage of glaucoma. Damage to the optic nerve is permanent and can not be reversed. Some doctors believe that the more damage that has already occurred, the easier it is for further damage to develop. Once the optic nerve is totally destroyed, an eye can not detect light.
The optic nerve is located in the back of the eye, behind the pupil. Normally if one shines a light on the pupil, the pupil constricts. This makes it extremely difficult, if not impossible, to adequately examine the optic nerve's structure. Our doctors, therefore, need to put dilating drops in the eye. These drops temporarily enlarge the pupil, or the window to the optic nerve, and usually last a matter of hours. They not only make things seem brighter, but can also cause images to seem blurrier.
The doctors need to examine both the way the optic nerve looks and the way it functions. This helps them decide whether there is glaucoma, and whether there has been any change or damage to the optic nerve. The doctor will either sketch the appearance of your optic nerve, take photographs of it, or both.
The doctors measure the function of your optic nerve by having you perform a visual field test. This test measures your side vision. This is important because the area of visual loss begins in the side vision and is not noticed by patients until glaucoma becomes very advanced. Our doctors hope to stop the damage before it gets very advanced, or if you already have advanced damage, we hope to prevent it from worsening.
Visual field testing requires a great deal of concentration. The test is designed to detect the dimmest light that you can see. You will only see one-half of the objects presented by the machine. This can be frustrating and frightening. It is also a boring test. Remember, if you are having trouble with the testing, or are tired, ask the technician to stop and explain the test to you again, or give you a rest!
If glaucoma worsens, visual field defects get larger and leave a patient with tunnel vision, not being able to see things to the side. It can cause a person to bump into objects or stumble and fall.
Under proper management and with good patient cooperation, it is very unlikely for a patient to go blind from glaucoma. Careful follow-up and good patient compliance severely limit the risk of marked visual loss.
Many different types of optic nerve imaging are available and we use many of them to help us make the diagnosis and to follow your eyes ensuring there is no progression.
Everything in life has risks! Our doctors would only treat glaucoma if they believe that the risks of not being treated and going blind are greater than the risks of any therapy. Our doctors take into account at least the following when deciding upon the appropriate course of action:
- How advanced the glaucoma is in each eye
- Family history of eye problems
- Other eye problems excluding glaucoma
- Life expectancy
- Life style
- Visual needs
- Medical history
- Medications for other diseases
- Allergies to medications
- The degree of damage from glaucoma
- The rate at which the glaucoma has progressed or is progressing
- The degree of damage caused by glaucoma which is already present in the eye before the beginning of therapy
Dr. James McManus or Dr. Jason Darlington will then decide what is the best option for you. We will discuss the alternatives with you as any decision is a team decision, between both you, your family, and the doctor. We will discuss the appropriate options, both the positive and negative aspects of each. We take all options seriously, knowing that there are risks and benefits to all therapies.
Choices for Therapy
Your initial choice of therapy will most likely be between medical eye drop therapy, SLT Laser Therapy or the iStent, although if the first one does not work, you can always try the other. It is important that you understand both types of therapy so that you can make the best decision for yourself.