Glaucoma (pronounced "glawkoma") is an eye disease that causes progressive damage to the optic nerve, the part of the eye responsible for carrying visual information from the retina to the brain. Because it affects peripheral (side) vision before central vision, glaucoma is usually not noticed until very late in its course.
Glaucoma affects people of all ages and races, including more than three million Americans and 67 million people worldwide. At least half of these people are unaware they have the disease. If left undetected and/or untreated, glaucoma can cause blindness. Glaucoma is a leading cause of blindness mainly because it usually does not present symptoms until permanent severe damage has occurred.
Vision destroyed by glaucoma cannot be restored, however, appropriate treatment can generally halt progression of the disease. Therefore, detection via periodic examinations is essential, especially after age 35. Glaucoma usually runs in families, involves both eyes, and occurs after middle age. It affects about five to seven percent of all Americans beyond age 65, and has an even higher rate of incidence in the black population. In rare instances, glaucoma may be present at birth, requiring prompt surgical attention.
Glaucoma is caused by a variety of factors, including changes in the optic nerve that make it more susceptible to damage, and often (but not always) an increase in pressure inside the eye.
To understand the anatomy involved, the front part of your eye is filled with a clear fluid ("aqueous humor") that supplies essential nutrients to tissues inside the eye and helps to maintain normal pressure for its shape. This fluid is constantly produced inside your eye by a structure called the "ciliary body," and later leaves via tiny drainage canals in a fine meshwork located in the "angle" between the cornea and the iris. (This fluid system should not be confused with tears, which are produced outside the eye and are not related to glaucoma.)
If this fluid system is working correctly, the proper amount is continually pumped into the eye and drained out. But, if the fluid is unable to flow away freely, pressure can rise inside the eye. This elevated pressure may be minimal, but if it persists over time, in some people it can damage the optic nerve, thus affecting how visual information is carried from the retina to the brain. This damage is characterized by a change in the size and shape of the optic cup, a depression in the optic nerve (see photos). At first, glaucoma only affects side vision, gradually constricting the field of view. But, if not treated, it can destroy all vision, resulting in blindness.
Primary Open-Angle Glaucoma is the most common form, accounting for the vast majority of cases. It normally occurs in both eyes and progresses so slowly that it often goes unnoticed for months or years—thus earning the title "Sneak Thief of Sight." With open-angle glaucoma, the filtration (drainage) angle of the eye between the cornea and iris (colored part) remains wide open, but some blockage occurs in the "trabecular meshwork" (the tiny sieve-like drainage canals through which eye fluid passes into the bloodstream). This backup creates increased intraocular (inner eye) pressure and gradual deterioration of the optic nerve. Primary open-angle glaucoma is a lifelong condition that, at present, can only be controlled, not cured.
Acute Angle-Closure is a much rarer form of glaucoma. In most of these patients, the filtration angle of the eye is unusually narrow. Thus, if something triggers the pupil to dilate too far in an affected eye, the iris balloons forward and adheres to the cornea—completely blocking the drainage of fluid at the outflow angle. This causes a rapid and extreme rise in pressure, which can lead to irreversible loss of vision without prompt medical and laser treatment by an ophthalmologist.
In contrast to open-angle glaucoma, acute angle-closure glaucoma has symptoms. It strikes suddenly (usually in one eye) and can cause severe eye pain or headaches above or around the eye, blurry vision, redness, and sometimes nausea and vomiting. An attack of acute angle-closure glaucoma is a medical emergency, and you should not wait to see whether or not it gets better on its own. The sooner this condition is diagnosed and treated, the greater the chance of reversing the episode.
Individuals at risk for acute angle-closure glaucoma can only be identified by examination. Antihistamines and antidepressants should be used with extreme caution in people who are susceptible to acute angle-closure glaucoma.
Key Differences Between:
Primary Open-Angle Glaucoma
Acute Angle-Closure Glaucoma
In this form of glaucoma, the optic nerve is so sensitive that even relatively normal intraocular pressures can damage the optic nerve, causing vision loss. Studies have proven that keeping the eye pressure in these people even lower than normal helps to reduce vision loss. However, some patients may continue to lose vision despite extremely low pressures.
This rare form of glaucoma occurs in infants and is secondary to improper development of the eye's drainage canals. Enlarged eyes, tearing and unusual sensitivity to light are common symptoms of congenital glaucoma and indicate the urgent need for examination.
This type of glaucoma is caused by some other condition or factor, such as inflammation of the eye, pigment dispersion, injuries, tumors, eye surgery, severe diabetes, or very advanced cataracts.
With this fairly common condition, patients have modestly elevated eye pressure but no sign of optic nerve damage. Since these people are at risk for developing true glaucoma in the future, their optic nerves, visual fields and pressures should be closely monitored.
The following information focuses on the diagnosis and treatment of primary open-angle glaucoma since it is the most prevalent form of the disease, and the type most people are familiar with when they use the word "glaucoma."
Because symptoms of open-angle glaucoma are often not noticeable until damage has already occurred, the best defense is an eye examination. It is also important to be aware of the following risk factors:
The factors usually evaluated in making a glaucoma diagnosis include:
The following instruments and tests may be used to examine the above factors:
Tonometry: Measures inner eye pressure by determining how much pressure is necessary to cause a slight indentation on the outer part of the eye. Depending upon the type of tonometry equipment used, a very small amount of pressure is applied by an instrument that painlessly touches the eyeball or by a warm puff of air that is directed toward the eyeball. Normal pressure usually ranges from 12-21 mmHG (millimeters of mercury). However, readings can vary by the hour or day. Some people may have borderline or mildly elevated pressures without any evidence of damage. This does not require immediate treatment, but does call for regular monitoring of pressures, visual fields, and optic nerve status.
Ophthalmoscopy: An instrument called an ophthalmoscope is used to check the optic nerve in the back of the eye for signs of glaucoma, including abnormal size and loss of pink coloring.
The above tests are a normal part of a routine comprehensive eye examination. Since glaucoma usually does not exhibit symptoms, periodic eye exams are important for anyone past age 35. If high pressures are found or the optic nerve looks unusual, one or more of the following tests may be performed:
Visual Field Testing: Creates a "map" of the field of vision using a computer-controlled instrument. The test involves sitting and staring straight ahead into a white, bowl-shaped area and pressing a button whenever a flash of light is seen anywhere in the bowl. The map produced by this test shows if there has been any loss of side vision (an early sign of glaucoma). Visual field tests are ordered upon diagnosis and are generally repeated every four months to two years, depending on the severity and level of control of the glaucoma.
Gonioscopy: A special hand-held contact lens with a mirror inside is used to examine the angle where the iris meets the cornea. This helps determine if the angle is wide and open (open-angle glaucoma), blocked and closed (angle-closure glaucoma), or clogged with pigment, debris or abnormal blood vessels (secondary glaucoma) and, therefore, what type of treatment is required. Gonioscopy is periodically performed in combination with pressure tests in those patients with open-angle glaucoma to assess whether or not the angle is remaining open.
Optical Coherence Tomography (OCT): Eye Care Specialists is pleased to join such prestigious eye institutions and research centers as Harvard Medical School and the Jules Stein Eye Institute in offering the latest advancement in glaucoma detection—Optical Coherence Tomography (OCT). With OCT laser scanning technology, we can create a "virtual reality" tissue biopsy (similar in concept to a CT scan) of the retina and optic nerve to detect and track signs of glaucoma, diabetic retinopathy, macular degeneration and other sight-threatening diseases often before any damage occurs.
Patients like the OCT because it is fast and painless. You simply rest your chin on a support and focus on a light while a safe, invisible laser scans the back of your eye to acquire an image in just seconds. The OCT then creates detailed computer printouts that provide unparalleled accuracy in visualizing and measuring the severity and extent of any changes to the optic nerve and retina.
As you return for follow-up exams, any telltale changes can be promptly detected and treated with the necessary drops, laser therapy or surgery—thus helping to prevent any future loss of vision.
The OCT is an advancement in glaucoma care because changes in your optic nerve can be accurately detected much sooner and easier than by traditional testing or visual inspection. For example, an air puff test is commonly used to measure intraocular pressure to diagnose glaucoma. Studies now show, however, that many glaucoma sufferers don't have elevated pressures. As a result, if you rely only on an air puff test, you may miss catching the disease in its early stages.
Conversely, elevated eye pressure doesn't always require treatment. If there is no evidence of optic nerve damage or field loss and pressures are only mildly elevated, repeat OCT tests may be recommended. In these cases, the OCT is used to track "glaucoma suspect" patients, allowing them to wait until it is truly necessary before having to start any medications.
Another benefit of OCT scanning is that, unlike some other forms of vision testing, it is not influenced by external stimuli, such as patient attention span, comfort, ability to follow directions, etc. Also, OCT technology uses an exact scanned image to detect glaucoma prior to experiencing any vision loss. This differs from visual field tests, which produce a plotted "map" representing a person's range of sight based on what areas have already been lost. (About 50 percent of nerve fiber must be lost before the damage appears on a visual field printout.)
Because of these many capabilities, the information gained from a single OCT scan is often more useful than any other diagnostic tool.
In addition to undergoing the above tests, it is important that you provide your doctor with an accurate medical history, including any vision concerns or symptoms. Since glaucoma may be hereditary, note any family members with the disease. You should also list all medications you use, as certain allergy and cold remedies and antidepressants can cause vision-threatening reactions in people with narrow angles.
At present, open-angle glaucoma cannot be prevented or cured. Fortunately, however, of the many causes, one factor can be controlled—inner eye pressure. With the most common type of glaucoma, fluid in the eye is able to reach the internal drainage channels, but has a difficult time getting through the tiny pores of the trabecular meshwork. The following methods of treatment are used to control the resulting increased pressure.
Glaucoma is most commonly treated with one or more of the following prescription medications that either slow the production of fluid in the eye or improve the flow through the drainage meshwork. In some cases, glaucoma can be well controlled with as little as one drop per day.
Glaucoma is usually well controlled with medications. For some patients, however, laser treatment may be a better alternative or may be used in conjunction with drops. Because of the expense and inconvenience of using many different types of drops, laser therapy may be implemented before a second or third drop is tried. Occasionally, it is used as the first method of treatment.
Glaucoma laser treatment is about 80 percent effective in significantly dropping pressure, and side effects are quite rare. Laser treatment is a painless outpatient procedure that uses a high-energy light beam to open the spaces where fluid leaves the eye. It is usually performed in two 10-minute sessions while sitting at a special microscope similar to the one used to examine your eyes.
For the minority of glaucoma patients who cannot be controlled with drops, pills or laser treatment, surgery is required to create a new opening for fluid to leave the eye. This is performed at our outpatient eye surgery center, typically under local anesthesia. As with any surgery, this procedure runs the risk of complications. The advent of newer techniques and medicines that retard scar formation, however, have significantly increased the success rate of filtering surgery.
Eye Care Specialists is pleased to offer qualified candidates Endoscopic Cyclo-Photocoagulation (ECP)—a breakthrough surgical laser procedure that has proven to be highly effective in both controlling glaucoma and reducing (or eliminating) the need for glaucoma drops. During the 10-minute ECP procedure, a self-sealing micro-incision is made to insert a small laser probe. This probe uses tiny optical fibers to illuminate, view and apply laser energy directly to the eye's "ciliary body" to reduce its fluid production and thereby lower glaucoma pressure. Since the natural lens inside the eye blocks access of the ECP probe to the ciliary body, the procedure can only be performed with or after cataract surgery—once the natural lens (cataract) has been removed.
Exciting new innovations are on the horizon for glaucoma diagnosis and treatment. Advancements are being made in developing eye drops with fewer side effects that can be used fewer times per day. Doctors are also working on new procedures to replace the filtering surgery operation, and scientists are looking at ways to genetically identify people apt to develop glaucoma. The most exciting frontier is the development of drugs to strengthen the optic nerve and make it more resistant to damage.
Blindness due to glaucoma takes a terrible toll on patients, their loved ones and society in terms of quality of life and financial burden. This loss is even more devastating if it is preventable. Therefore, since symptoms usually do not appear until damage has already occurred, periodic glaucoma examinations are crucial. Early detection and treatment are still the best methods to control the disease and to help ensure that everyone has the opportunity to see life to the fullest.
Since 1985, Eye Care Specialists has provided comprehensive medical, surgical and laser care for virtually every eye condition to more than 121,000 people in southeastern Wisconsin. If you would like detailed booklets/handouts on the information contained in this section or other eye-related topics, please contact our Communications & Education Department at 414-321-7035. To schedule a comprehensive eye evaluation, call one of our three convenient Milwaukee-area locations shown at the top of this web page.
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