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Home | Eyecare | Eye Health | Glaucoma
 More articles related to Glaucoma
 SpotLight : Glaucoma
What is glaucoma?
Glaucoma is a disorder of the eye which can cause vision loss and blindness due to the pressure being too high inside the eye. The end result of the pressure being too high is that the optic nerve, which is the main nerve providing vision to the eye, can become permanently damaged. Once the optic nerve is damaged, vision is typically lost. Vision loss is usually in the peripheral or side vision and then progresses towards the center of the vision. This can create "tunnel" vision in the patient with advanced glaucoma.
What are the types of glaucoma?
There are many different types of glaucoma such as congenital glaucoma or pigmentary glaucoma, but, in general we can divide most glaucoma cases into two categories: chronic glaucoma and acute glaucoma. Chronic open-angle glaucoma (COAG) is the most common type in the United States. The cause of COAG is not known, but it is thought that there is a problem with the drainage portion of the eye, called the trabecular meshwork. The incidence of COAG increases with age and, therefore, it is felt that there is an anatomic change in the meshwork due to an aging process which causes the problem with drainage of fluid from the eye. This leads to the increased pressure in the eye associated with COAG. There are usually no symptoms with COAG.
The other major type of glaucoma is called acute angle closure glaucoma (ACG). This type of glaucoma is different from COAG in that the pressure rise inside the eye is very rapid and markedly higher than with COAG. Because of the rapid rise in pressure the patient experiences severe eye pain and redness, blurred vision, headache and also nausea and vomiting. The cause of this dramatic pressure rise is usually because the eye is anatomically shorter than normal which allows the iris (the colored portion of the eye) to move forward and block the drainage of the fluid into the trabecular meshwork. When this occurs, there is no place for the fluid to go and the pressure builds up inside the eye very rapidly. This is an emergency and if the pressure is not relieved quickly, the patient may lose all the vision in the eye. Treatment usually involves both oral and topical (drops) medication along with performing a laser to allow the fluid another pathway to drain from the eye. Sometimes, when the laser cannot be performed, emergency eye surgery is required to solve the problem.
How is glaucoma diagnosed?
Glaucoma usually can only be diagnosed by a thorough medical eye exam. There are typically no symptoms with glaucoma, especially in the open-angle type. By examining a patients eye, the physician can determine if the pressure is too high, and/or if the optic nerve appears damaged. Many times a patient's pressure can be read as normal and he may still have optic nerve damage and glaucoma. This is because the pressure in the eye can fluctuate and be high at one time in the day (typically it is higher in the morning) and normal at another time during the day. Also, some patients can develop glaucoma even if the pressure is always normal. This is a special category of glaucoma known as low-tension or normal-pressure glaucoma. This type usually occurs in more elderly patients and is thought to be due to poor blood flow to the optic nerve which, thus, damages the nerve. This type of glaucoma is difficult to treat.
A special type of test known as a visual field is often used to aid the physician in diagnosing and monitoring glaucoma. This test utilizes a computerized technique to measure the peripheral or side vision. Specific small defects in the peripheral vision can be an early indicator of glaucoma. If the defect enlarges over time, this usually indicates that the glaucoma is getting worse. Other tests which may be performed include stereo photographs of the optic nerves which can show if optic nerve damage (referred to as "cupping" of the optic nerve) is worsening over time. Several new tests are on the horizon which hopefully will make the diagnosis and management of glaucoma easier in the future.
How is glaucoma treated?
When glaucoma is suspected in a patient, a period of observation is usually warranted. During this time, the physician will typically monitor the patient's eye pressure, sometimes having the patient come in at different times during the day to help establish what the patient's maximum pressure reading is. This period of observation can vary widely from patient to patient. It can range from just a few weeks to as long as several years. Patients who are at higher risk for developing glaucoma will be followed at more frequent intervals (for example, every 3 months).
Using Eyedrops for Glaucoma
When glaucoma is definitely diagnosed, patients will usually be placed on eye drops to control the eye pressure. Very often, the physician will start the patient on a drop in just one eye, leaving the other eye untreated. This is called a one-eyed trial, treating one eye and using the other eye as the control eye in order to see if the medication is actually effective in lowering the pressure in the treated eye. Once the medication is found to be effective, it is usually started in the other eye. The choice of the type of medication is generally a decision made by the physician after discussing the medication's side effects with the patient. Certain glaucoma drops can cause problems with the heart or lungs and are usually avoided in patients with these types of health problems. Several glaucoma medications have been released recently which markedly reduce the possible systemic side effects caused by other medications while being very effective at lowering the eye pressure. These include latanoprost (Xalatan?) and bromonidine (Alphagan?). These two-medications are quickly becoming the first line drugs in the treatment of glaucoma.
Since there are now over six different classes of medications used in the treatment of glaucoma, the chances of success in lowering the pressure has been greatly increased. But, in some cases, eye drops by themselves cannot always lower the pressure enough for certain patients. Other treatment modalities which are used include oral medication, lasers and filtration surgery. Oral medications are not used very often any more mainly because of the systemic side effects they cause and because usually if the patient fails drop therapy, the physician will usually move onto laser and surgical therapy.
Laser Surgery for Glaucoma
Two different types of laser procedures are utilized to treat glaucoma. The first, called Laser Peripheral Iridotomy (LPI) is used to treat narrow angle glaucoma or acute angle closure glaucoma. With LPI, a small hole is placed in the iris to allow the fluid inside the eye a new passage to exit the eye. This procedure is usually used as a prophylactic treatment to prevent acute angle closure glaucoma in a patient that has anatomically narrow angles in the eyes. A second laser procedure, known as an Argon Laser Trabeculoplasty (ALT) is used in open angle glaucoma to reduce pressure. During the procedure an argon laser is used to place small burns in the trabecular meshwork, the drainage portion of the eye. By doing this, the meshwork is thought to open adjacent, non-burned areas to allow fluid an easier passage way out of the eye.
Filtration Surgery for Glaucoma
Laser treatment is sometimes unsuccessful or only temporarily lowers the pressure. In those patients that need even lower pressure or who have failed both drug treatment and laser therapy, a surgical procedure called a filtration operation is usually recommended. In this procedure, the surgeon creates a small flap of tissue on the sclera (the white part of the eye). An incision is made into the front portion of the eye, called the anterior chamber, which allows the fluid inside the eye a new passage out of the eye. The fluid then filters out of the eye underneath the conjunctiva (the clear membrane over the sclera). This procedure usually lowers the pressure in the eye significantly, thus reducing the risk of further nerve damage inside the eye. Filtration operations have the risks associated with introcular surgery such as infection and bleeding, plus, they can fail after a certain length of time. To reduce the risk of failure, anti-metabolite medications (used in cancer therapy) are often used to decrease scar formation.
Visual Field Test
The visual field is the entire area one can see. It includes central and peripheral (side) vision. A visual field test can detect problems with vision in any part of the visual field. Changes in the visual field may be difficult to notice since both eyes are generally used at the same time. One eye can sometimes compensate for some vision loss in the other. A problem may not be detected until each eye is tested separately.
The visual field test provides information that no other test can. It is used to detect many diseases, such as glaucoma or retinitis pigmentosa, which affect the eye, optic nerve, and brain. It can also help diagnose brain tumors, stroke and other conditions. Visual field testing helps diagnose the disease and can follow the progress of the disease and its treatment.
During a visual field test, one eye is temporarily patched while the other eye is being tested. You are asked to look straight ahead at a fixed spot and watch for targets to appear in your field of vision.
There are two kinds of visual field tests. One method uses moving targets. Targets are moved from outside the visual field (where you can't see them) toward the center of your vision. When you see them, you press a button. The test can be done using a dark screen on a wall (called tangent screen testing) or using a large bowl-shaped instrument (called Goldmann testing).
The other testing method uses small fixed targets that appear briefly as bright or dim lights (called computerized static perimetry). You sit in a chair facing either a bowl-shaped instrument or a computer screen and indicate when you see the targets appear.
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