What is Glaucoma?
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 more than 4 million Americans of all ages and races. At least half of these people are unaware that they have the disease. If left undetected and/or untreated, glaucoma can cause permanent loss of vision. Glaucoma is a leading cause of blindness mainly because it usually does not present symptoms until permanent severe damage has occurred.
Glaucoma can increase the risk of falls and car accidents due to the “tunneling” of vision. Vision destroyed by glaucoma cannot be restored, however, appropriate treatment can generally halt progression of the disease. As such, detection via periodic comprehensive examinations is essential, especially after age 35.
Too much fluid stays in the eye, which causes pressure to rise.
High pressure damages the optic nerve, which carries information to the brain
Drainage canal is blocked.
What Causes Glaucoma?
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 continually 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 reduces the blood supply to the optic nerve, thus damaging 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.
Inner eye pressure caused by glaucoma can damage the optic nerve, thus affecting how visual information is carried from the retina to the brain.
Types of Glaucoma
Primary Open-Angle Glaucoma (POAG)
This is the most common form of the disease, accounting for the vast majority (up to 90 percent) of cases. POAG normally occurs in both eyes and progresses so slowly that it often goes unnoticed for months or years—thus earning it 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 Glaucoma
This is a much rarer but extremely serious 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.
Other Forms of Glaucoma
There are four other less common types of glaucoma.
Low-Tension 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.
Congenital Glaucoma: 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.
Secondary Glaucoma: 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.
Ocular Hypertension: 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 (POAG) 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:
Heredity: Siblings and children of glaucoma patients have a 5-10 times greater risk of developing the disease and should be screened every 1-2 years.
Age: After age 35, the chance of developing open-angle glaucoma increases with age. About 2% of people ages 40-50 and 8% age 70+ have elevated inner eye pressure.
Diabetes: Diabetics have a three times greater risk of developing glaucoma than non-diabetics.
Ethnicity: Black people have a 6-8 times greater risk of losing vision to glaucoma than white people. They also often develop it at an earlier age. Latinos and Asians also have higher risk rates.
Medication: Cortisone use (by mouth, inhalation or eye drops) increases the risk of developing glaucoma in certain susceptible individuals.
Eye Injuries or Surgery: A history of injuries or surgery to the eye warrants periodic glaucoma check-ups.
Nearsightedness: People who need glasses to see in the distance are at a slightly greater risk for developing open-angle glaucoma.
Tunneling caused by glaucoma can happen so gradually that it is not noticed until permanent sight loss has occurred.
Usually there are none. As noted above, the most common type of glaucoma is painless and progresses so slowly that most people don't notice symptoms for months or years—until significant permanent damage has already occurred. Glaucoma affects 4+ million Americans, and up to half don't even know they have it. That's why regular eye exams are vital to protecting vision. After age 40, every two years, you should have a comprehensive eye exam that includes a check for glaucoma, especially if you have risk factors.
Detection & Monitoring
The following factors are usually evaluated in making a glaucoma diagnosis:
Intraocular (inner eye) pressure
Optic cup appearance (along with the following to evaluate the health of the optic nerve)
Optic Nerve fiber layer changes
Field of vision losses
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 (millimetres 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 look through the pupil and light up the back of the eye to check the health of the retina and optic nerve. With this device, signs of glaucoma (like abnormal optic cup size and loss of pink coloring) can be detected.
Tonometry and ophthalmoscopy are normal parts of a routine comprehensive eye examination. Since glaucoma usually does not exhibit symptoms, periodic eye exams are important for anyone past age 40. If high pressures are found or the optic nerve looks unusual, one or more of the following tests may be performed:
Visual Field Testing: During this test, the patient sits and stares straight ahead into a white, bowl-shaped area and presses a button whenever a flash of light is noticed. The device then produces a computerized “map” that 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 patients with open-angle glaucoma to assess whether or not the angle is still open.
Optical Coherence Tomography (OCT): Eye Care Specialists was one of the first practices in Wisconsin to offer this advancement in glaucoma detection. With OCT laser scanning technology, we can create a “virtual reality” tissue biopsy of the retina and optic nerve to detect and track signs of glaucoma, diabetic retinopathy, macular degeneration and other sight-threatening diseases before any damage occurs.
Patients like the OCT because it is fast and painless. You simply rest your chin and focus on a dot while a safe, invisible laser light scans the inside of your eye. The OCT then creates detailed printouts (similar to CT scans) 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. For some patients, there may be no evidence of optic nerve damage or field loss and pressures are only mildly elevated. In these cases, repeat OCTs and visual fields are typically recommended to track the "glaucoma suspect" and thus allow them to wait until it is truly necessary before having to start any treatment.
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.
Ways to Control Glaucoma
At present, open-angle glaucoma can NOT 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 prescription medication eye drops that either reduce fluid production in the eye or increase outflow through the drainage meshwork. In some cases, glaucoma can be well controlled with as little as one drop per day.
Laser & Surgical Treatment
Glaucoma is usually well controlled with medications. In cases when drops alone cannot control pressure, or side effects are intolerable, or multiple types of drops are required, outpatient laser or surgical treatment may be an alternative. SLT (which increases fluid drainage) and ECP (which decreases fluid production) laser procedures take less than 10 minutes to perform and are covered by Medicare and most insurance plans. Eye Care Specialists' surgeons also utilize a growing number of new Minimally Invasive Glaucoma Surgery (MIGS) procedures to improve the eye's drainage system,
These advanced procedures are often successful at controlling glaucoma and reducing the need for prescription drops. This is especially important for people who already have other conditions requiring daily medications that they have to worry about buying, taking and tracking. These treatments also typically have low complication rates and can sometimes be repeated, if needed.
Deciding when or whether to use medication, laser and/or surgical treatment depends on careful evaluation of your specific condition. Candidacy, benefits and risks will be discussed with you by your eye care specialist.
Rules to Follow
Schedule regular exams/screenings for you and your family. Early detection and treatment are the best means to control glaucoma and prevent permanent sight loss.
Take drops and medications as directed. Do NOT use more or less than prescribed.
Keep all eye appointments and use your drops as normal on those days. If you don’t, your pressures may be affected and your doctor won’t be able to tell how you are doing.
Schedule drops and medications around daily routines, like bedtime and meals, to help remember to use them.
If you forget to use your drops, administer them as soon as you remember. Then return to your regular schedule.
Glaucoma-related blindness creates physical, emotional and financial burdens for patients, families and society. This loss is even more devastating if it was preventable. Since symptoms usually do not appear until permanent damage has already occurred, periodic glaucoma examinations are crucial. Early detection and treatment are still the best means to control glaucoma and to help ensure that everyone has the opportunity to see life to the fullest.
For more information or a comprehensive examination . . .
Since 1985, Eye Care Specialists has provided comprehensive medical, surgical and laser care for virtually every eye condition to more than 185,000 people. If you would like our free educational booklet on the eye concern reviewed above, please complete this form or call our Communications & Education Department at 414-321-7035. To schedule a comprehensive eye examination or a second opinion evaluation, call any of our three convenient Milwaukee-area locations directly.