Glaucoma

Glaucoma is the leading cause of preventable blindness in the United States. Loss of vision and/or peripheral field from glaucoma is permanent and irreversible. Therefore, the only treatment that can be instituted is early diagnosis and therapy.

Glaucoma is often known as the "sneak thief of sight" because it doesn't cause symptoms until late in the disease. It is estimated that approximately 15 percent of all blindness is related to glaucoma and that is not even taking into account all of the disability it causes.

Glaucoma is believed to be present in at least five percent of the population over 40 years of age. Glaucoma can be found in children and young adults, though it is less common in these age groups. It is also estimated that at least 50 percent of people who have glaucoma go undiagnosed.

It is essentially a disease in which abnormally high pressure in the eye causes damage to the nerve head. This pressure is not related to blood pressure or any other pressure in the body. There are many different types of glaucoma. Some are known as chronic simple glaucoma, angle closure glaucoma or secondary glaucoma, but the mechanism of visual loss is all the same. Pressure in the eye rises, therefore causing damage in the back of the eye (the optic nerve).

Glaucoma does run in families and is more commonly found in family members of a glaucoma patient than in the general population. It is also far more frequently found in patients with diabetes. People who are very nearsighted also have an increased incidence of glaucoma. Eyes that have received trauma or injury and have developed difficulty in the outflow mechanisms are subject to glaucoma. Patients who have vascular problems are also at a greater risk for glaucoma. Glaucoma usually occurs statistically in people after 40 years of age, but it can also occur in infants and teenagers as well.
Mechanism of Glaucoma

The eye has its own separate and unique pressure system. The ciliary body produces a water-like substance know as aqueous humor, which passes forward through the pupil and into the anterior chamber of the eye. It then leaves the eye through a sieve-like structure known as the trabecular meshwork. It eventually percolates through to be mixed into the blood. The two basic mechanisms that can produce glaucoma are either excessive production of fluid or decrease in the outflow facility of the drainage system. In open angle glaucoma, the drain or the trabecular meshwork is not functioning well and the fluid cannot get out as fast as it is being produced, thus causing a rise in pressure in the eye.

In closed angle glaucoma, the "angle" that approaches the meshwork is narrow. Though the meshwork or drain may be functioning adequately, the approach is too thin and the fluid cannot reach the drain in adequate volume to lower the pressure in the eye. If these two forces are in proper balance, the intraocular pressure remains below "20" mm of mercury, as measured by applanation tonometry. As the pressure rises above this "normal" range, nerve cells and fibers can be damaged in the back of the eye, which slowly causes progressive loss of side vision. As the pressure continues, the optic nerve will be destroyed to a large extent and eventually will decrease central visual activity. Though there are many subdivisions of glaucoma, they can basically be divided into open angle and narrow angle glaucoma.
Open Angle Glaucoma

Open angle glaucoma is the most common form and accounts for about 90 percent of all glaucoma. This is where the aqueous fluid reaches the trabecular meshwork outflow facility of the eye but does not drain as effectively as it should; therefore, the pressure will rise. This is a disease that, over many years, will cause slow progressive decrease in the peripheral field of vision and, therefore, ultimately blindness. The inherent danger of this condition is that there are no symptoms. People are not aware that the pressure is elevated until permanent visual field loss has occurred.

Treatment consists of either decreasing the amount of fluid produced or increasing the facility of outflow of the eye and allowing more fluid to escape. Drops, pills, laser treatments or surgery can do this.
Narrow Angle

Narrow angle glaucoma is a less common form and occurs in people who have an anatomically narrow anterior chamber eye angle. This "narrow angle" blocks the fluid from ever reaching the meshwork or "drain." The eye pressure remains normal until an "attack" occurs. There is an acute rise of pressure when the iris comes forward and closes off the flow of the aqueous fluid to the trabecular meshwork outflow. The intraocular pressure rises abruptly to very dangerous levels and causes excruciating pain, headache, a red eye, blurred vision (especially at night), colored halos around lights, nausea and vomiting.

Treatment of acute angle closure glaucoma is a medical emergency and requires hospitalization. Usually, surgical or laser therapy is then necessary to cure the attack. The aim of treatment is to prevent an acute attack from occurring and, with laser therapy, "open the angle" before it "closes" up.
DIAGNOSIS

Glaucoma can also come as a result of an enlarged cataract, vascular disease or inflammations within the eye. These are known as secondary glaucoma.

The inherent risk of glaucoma is the fact that, without having an ocular examination, one cannot be assured of having normal intraocular pressure.

Glaucoma pressure is most accurately measured by an “application” tonometer that is “pushed” against the eye and the responsive pressure is measured.

In addition to this pressure reading, one must examine the optic nerve to detect any abnormalities or asymmetry between the two eyes, look for areas of dead nerve fibers and atrophy. The other parameter that is very useful is a visual field. This measures the peripheral vision (side vision). This is usually how doctors find the first evidence of glaucoma damage. This can be done with a Goldman perimeter, automated perimeter or a central field tangent screen test. It is also needed to measure. Additional testing to diagnose and manage Glaucoma:

1. Corneal Nerve Tomography – Which is a computerized measurement of the optic nerve that can be compared from visit to visit to detect change.
2. Visual Field
3. Corneal Thickness (Pachemetry)

These measurements are done as stereoscopic views and give us a good view of the optic nerve.
TREATMENT

Considering all these factors, we can then best advise you if you are at risk or have glaucoma. If you have glaucoma or are at risk, you will either be given medical therapy or watched more closely. If medical therapy is ineffective, then your options consist of a new technique called laser trabeculoplasty or gonio photocoagulation, or surgery. This laser has been proven to be extremely successful in the treatment of glaucoma. This technique requires placing 50 micron spots of laser burns into the trabecular meshwork, where the fluid flows out of the eye. This lasering of the trabecular meshwork helps open and therefore allows more drainage of the fluid.

In addition to these methods, if not successful, the other alternative is surgery. There are various types of surgery that can be done.

The most important factor in the treatment of glaucoma is early detection.  It is essential for people, especially over the age of 40, to have routine eye exams and dilated fundus exams to evaluate the optic nerve and the pressure by applanation tonometry. It is only by careful inspection and close examination that early detection of this disease can be affected.

By early detection of this disease, we are able to control and monitor the progression of glaucoma. Open angle glaucoma is not a curable disease.

The purpose of all treatment in glaucoma is to prevent further rises in pressure and maintain pressure to a point where there will not be further damage to the optic nerve or to the visual fields.

Once again, we emphasize that the most important aspect of glaucoma is the diagnosis of it and the implementation of therapy as soon as the disease can be recognized.
LASER TREATMENT OF GLAUCOMA

Laser iridotomy has rapidly become the procedure of choice in the treatment of angle closure glaucoma because of the combination of ease and convenience for both the patient and the surgeon and the infrequent occurrence of severe complications. Laser iridotomies are painless. There are no restrictions after receiving the treatment and complications are rare.

Treatment for closed angle or narrow angle glaucoma include laser iridotomy, drops or surgery.

The advantages of laser iridotomy are:

1. The procedure is easy and conveniently performed on an outpatient basis.
2. The complication rate is extremely low.

The purpose of the laser iridotomy is to create a hole to allow more fluid to reach the drain. This hole will prevent future attacks of angle closure glaucoma and can cure this condition. An analogy to this is comparing the eye to a sink in which the faucet is on and the drain is open. Angle closure is similar to putting a rubber stopper over the drain, causing the water level (pressure) to rise. Laser iridotomy creates a hole in the stopper and allows the drain to re-open. Assuming that there is no damage to the drain or the outflow mechanism or trabecular meshwork, this will successfully treat angle closure. It is possible that more than one session may be necessary either for re-opening the site as the pigment proliferates, to increase the size or to totally penetrate the opening. It is possible to get a rise in pressure after this procedure.

Argon laser trabeculoplasty is a procedure using an argon laser to treat the trabecular meshwork to open up the drain to allow more fluid to leave the eye. It is used when maximally tolerated medical management has failed to provide adequate glaucoma control.

It is essential that the patient understand the following points:

1. The purpose of the laser is to lower the intraocular pressure and to protect the eye from further damage.
2. Glaucoma medications will probably be necessary after the laser.
3. Argon laser trabeculoplasty will not improve vision although it may help to preserve it.
4. The reason laser surgery is necessary is that the glaucoma cannot be controlled on tolerated medical therapy. The hope is that after the ALT, at least with medications, the pressure can be maintained.
5. If the laser is not 100% successful, a microsurgical glaucoma operation may be necessary.
6. Very close follow-up is required immediately following laser surgery.
7. It takes at least a month to determine how much of the pressure drop will occur as a result of the laser glaucoma operation.
8. A transient pressure rise may occur following surgery. This does not necessarily affect the end result one way or the other.

Patients who receive an Argon Laser Trabeculoplasty should continue pre-operative medical regime. Steroid medication will be given to you as directed to decrease the inflammation as a result of the procedure. There are no limitations of physical activity. There may be some blurring of vision for a short period. There may be a transient elevation of pressure rise. If the pressure does not satisfactorily lower, surgery may be needed.

For any additional information or questions, you can always reach the office 24 hours a day, 7 days a week at (619) 697-4600.