Page: 6e1
Back:Hobby (6e)
Next:Hobby (6e)
Table of contents:
Common Types
Risk Factors

Common Types of Glaucoma
Primary open angle glaucoma
The vast majority of patients with glaucoma in the western hemisphere have primary open angle glaucoma. This means that the eye otherwise looks normal except for the optic nerve damage. Other types of glaucoma have the same optic nerve damage, but the eye has other abnormal features. Examples of these "secondary" glaucomas include exfoliation glaucoma and pigment dispersion glaucoma. Other common types of glaucoma include angle closure glaucoma and neovascular glaucoma. The treatment for these last two conditions is different than for primary open angle glaucoma. 
Exfoliation glaucoma
Exfoliation glaucoma is a form of open angle glaucoma. It is distinguished from primary open angle glaucoma by the presence of abnormal deposits on the surface of the lens and other structures. Eye pressure can occasionally rise very rapidly in eyes with exfoliation glaucoma. It tends to occur in older patients and is more common in persons of Scandinavian descent. The treatment of both conditions is similar to primary open angle glaucoma.
Pigment dispersion glaucoma
Pigment dispersion glaucoma is a form of open angle glaucoma. In pigment dispersion glaucoma, pigment is lost from the iris and is deposited on other structures, including the drainage channels. It is more common in younger patients, in males, and in near-sighted persons. It is treated with medications, laser, or surgery.
Closed angle glaucoma
In angle closure glaucoma, the structures in the front of the eye are too crowded together to allow the normal flow of aqueous fluid both within the eye and out of the eye. In particular, the aqueous fluid has difficulty passing from behind the iris (colored part of the eye), through the pupil (hole in the center of the iris) to the anterior chamber (fluid filled area between the iris and the cornea (clear front part of the eye through which light passes). As a result, the iris is too close to the anterior chamber angle, where the fluid drains. This predisposes the eye to two potentially harmful situations. In acute angle closure glaucoma, there is a rapid elevation in eye pressure. The patient often notices eye pain, eye redness, and blurred vision. Because the very high eye pressure can rapidly damage the optic nerve, acute angle closure is a true emergency and requires immediate treatment by an ophthalmologist. In chronic angle closure glaucoma, the drainage tissues gradually become scarred, and the eye pressure rises slowly. This condition is generally silent, and severe glaucoma damage can occur without the patient's knowledge.

The best way to avoid the problems of angle closure glaucoma is prevention. A careful eye exam that includes a technique called gonioscopy is the only way to determine if an eye is predisposed to angle closure glaucoma. In gonioscopy, a small lens is momentarily placed on the eye allowing the doctor to observe the drainage channels.
The treatment for eyes that have had an attack of angle closure glaucoma or are predisposed to acute angle closure is a laser procedure called a peripheral iridotomy.

Neovascular glaucoma
In neovascular glaucoma, abnormal blood vessels grow in the front part of the inside of the eye, blocking the drainage channels. This results in elevation of the eye pressure and damage to the optic nerve. The cause of the abnormal blood vessels is poor oxygen supply to the eye. The most common causes of neovascular glaucoma are diabetes, blockage of blood vessels in the back of the eye, and insufficient delivery of blood to the head due to blockage of the arteries in the neck.

Once neovascular glaucoma is fully developed, it is extremely difficult to treat, and most eyes sustain severe and permanent visual loss. Therefore, it is best to prevent it or treat it in its earliest stages. For diabetics, this means frequent eye exams, particularly if the retina has already been affected by diabetes (diabetic retinopathy). When there is blockage of blood vessels in the back of the eye, the patient generally notices sudden severe loss of vision, and this symptom should be evaluated promptly by an eye doctor. Blockage of an artery in the neck can sometimes produce symptoms of temporary loss of vision, speech, or weakness in an arm or leg. It can be detected in a general physical exam and sometimes by an eye exam.

Although eyedrops and pills may aid in the treatment of neovascular glaucoma, the most important treatment is laser treatment (scatter panretinal photocoagulation) to the retina in the back of the eye. For reasons not entirely understood, this laser treatment can cause the blood vessels to go away, and if too much damage to the drainage channels has not occurred, the eye pressure may return to normal. In eyes in which the eye pressure remains elevated despite laser treatment and medicine, a trabeculectomy or a ciliodestructive procedure may be performed.

How does the physician diagnose glaucoma?
Glaucoma is diagnosed by carefully studying the optic nerve and testing the field of vision. The optic nerve can be seen by the eye doctor with special equipment, after the pupils have been dilated. The hallmark optic nerve damage from glaucoma is abnormal "cupping". This refers to an abnormal depression in the center of the part of the optic nerve that is visible to the eye doctor. The presence of an abnormal amount of cupping leads the eye doctor to perform a visual field, or peripheral vision test, to help confirm the diagnosis. A peripheral vision test is an important part of the evaluation of glaucoma, because vision loss from glaucoma usually starts in the periphery. Based upon the results of the peripheral vision test and the appearance of the optic nerve, the doctor can state that you either have glaucoma, may have glaucoma, or do not have glaucoma.
Visual field (peripheral vision) testing
Along with the doctor's examination of the optic nerve, visual field testing is the most important aspect of the evaluation for glaucoma. It represents the best way currently to determine how well you see. Although we often refer to peripheral vision testing, in fact, the test evaluates how well you see close to the center of your vision.
Modern visual field testing involves the use of an automated (computerized) machine. A visual field technician stands by to make sure that the test runs properly. You will place your head in a large hemisphere, stare at a central target, and will signal when you see a light flashed.
The visual field test generally takes between 10 and 15 minutes per eye. Some of the lights are intentionally quite dim and you will not be sure if you saw them or not. Many patients worry that losing attention during the test or being anxious during the test will make their results worse. The visual field machine, however, carefully checks for how well you are able to pay attention and give consistent responses. In that way your doctor can take this into account in interpreting the results.
Because we are all human, there will be variations from day to day in our visual field exam, especially the first couple of times that we take the test. This variation explains why your doctor may want several tests to determine if you have glaucoma or if there has been a change in your peripheral vision.
Patients who are being followed for the possible development of glaucoma may have visual field testing once or twice a year; certain patients may need to have visual field testing as often as 4-6 times a year. Remember, although important, visual field testing is only one of several ways that the doctor uses to determine the status of your glaucoma.

Risk Factors for the Development of Glaucoma

The most important risk factors for the development of glaucoma are a high intraocular pressure, black race, and advancing age. A positive history of glaucoma in a first degree relative (parent, child, but particularly a sibling) also increases the likelihood of having or developing glaucoma. High blood pressure, diabetes, and near-sightedness may be additional risk factors.

Treatment of Glaucoma

Glaucoma is a treatable disease. Glaucoma is treated by lowering the eye pressure by medicines, laser, or surgery. This reduces the likelihood that the eye pressure will damage the optic nerve. Decades of clinical experience and the results of clinical trials strongly suggest that treatment to lower the eye pressure can help prevent the development of glaucoma damage and slow the worsening of glaucoma damage that has already occurred.
It must be emphasized that for all intents and purposes, glaucoma damage that has occurred can not be reversed. Therefore, the goal of treatment is the prevention of more glaucoma damage, not the reversal of pre-existing damage.

When to treat?

The decision to start treatment for glaucoma must be individualized for each patient. Treatment should be started when the benefits of treatment exceed the risks. In general, there are two situations in which treatment should be initiated.
First, if there is clear-cut glaucoma damage and the eye pressure is elevated.
Second, if there is no definite glaucoma damage, but the risk of developing glaucoma damage is high if the eye pressure is not lowered.
Glaucoma is a chronic disease that can be treated but not cured. Therefore, the decision to start treatment is a commitment to lifelong therapy. For this reason, it is important for both the physician and the patient to be comfortable with the need for treatment before it is started.
How much eye pressure lowering is enough?
One of the most difficult decisions in the treatment of glaucoma is determining how much the intraocular pressure should be lowered to avoid further damage to the optic nerve. The decision is difficult because optic nerves respond differently to the effect of high intraocular pressure. The physician will usually take into account the level of the intraocular pressure at which optic nerve damage occurred and the amount of damage already present in deciding on a "target" pressure for treatment.
Laser, medicine, or surgery first?
For the past fifteen years glaucoma therapy has started with medications, proceeded to laser treatment only when medications were ineffective, and resorted to surgery only when the other methods had failed. The Glaucoma Laser Trial has demonstrated that laser treatment can be as effective as medication, leading the American Academy of Ophthalmology to state that laser treatment is an appropriate alternative to medication as the initial treatment for primary open angle glaucoma. A multicenter trial is in progress to evaluate the role of surgery (trabeculectomy) as the initial treatment for glaucoma, but the results will not be available for several years.

The bottom line is that more and more patients and physicians may be opting for laser treatment before medications and for glaucoma surgery earlier in the course of treatment. Under any circumstances, the decision will remain an individual one between the doctor and patient.

Medical treatment consists of either eyedrops or pills. Many types of glaucoma medications are available for use. 

Beta-blocker eye drops have been in use for 20 years and have been used by millions of patients. They are used once or twice a day and are comfortable to use. They can make breathing and heart problems worse in patients with heart or lung conditions.
Three new classes of eye drops have come along in the last 5 years and have generated a tremendous amount of interest. Topical carbonic anhydrase inhibitors lower eye pressure in a fashion similar to the carbonic anhydrase inhibitor pills, but without many of the side effects. Prostaglandin eyedrops are highly effective in lowering eye pressure and only need to be used once a day. They can cause a small percentage of blue eyes to darken towards brown, but have very few systemic side effects. Alpha agonist eyedrops likewise are effective at lowering eye pressure with few side effects, but must be used two or three times a day. 

Epinephrine drops are used twice a day and can result in temporary redness of the eye and blurred vision. They have largely been replaced by the newer medications. Miotics have a green cap and are generally used four times a day. They can produce a brow ache when first used, and constrict the pupil. This can result in blurred vision in some patients. Because of these side effects, their use is diminishing.

Carbonic anhydrase inhibitior pills can be very effective in lowering eye pressure. Because they produce side effects in about 50% of patients, they are generally reserved for use when eyedrops (or laser) have not been sufficient. The most frequent side effects are tingling in the fingers and toes, fatigue, and loss of appetite. Less commonly they can cause blood chemistry imbalance and kidney stones. Extremely rarely they can cause aplastic anemia, a potentially fatal condition in which the bone marrow no longer produces blood cells.

How to take eyedrops
Administering eyedrops may take some practice. Perhaps the most important tip is to use the index finger of the hand that is not holding the bottle to pull down the lower lid. This forms a pocket into which the drop can be placed. If you are taking more than one type of eyedrop, 3-5 minutes should separate the application of the two drops. An important point to remember is that all eyedrops enter the blood stream and can potentially affect your whole body. The amount of eyedrop entering the blood stream can be decreased by closing your eyes after instilling the drop and by applying pressure on the skin between your eye and your nose.
Forum of Glaucoma 
Please visit my GLAUCOMA-FORUM... go to GLAUCOMA-FORUM (9e)
Back: Hobby (6e)
Next: Hobby (6e)