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Ophthalmology: Glaucoma

Glaucoma is a disease of the optic nerve, the part of the eye that carries images we see to the brain.

The front of the eye is filled with a fluid, called aqueous humor. This fluid is mostly water, and the main purpose is to inflate and maintain the shape of the eye. This fluid is very similar to water in a balloon, and sometimes the eye pressure can be too high. In such cases, pressure is placed on the optic nerve. This elevated pressure causes damage to the optic nerve. If the optic nerve is damaged, then vision cannot be transmitted from the eye to the brain, resulting in blindness. Unfortunately, damage to the optic nerve is not typically reversible. Once vision is lost, it cannot be restored. Therefore, screening and prevention are the keys to good glaucoma care. If detected, glaucoma is often treated with topical medications (eye drops), laser treatments or surgery.

There are many forms of glaucoma, but the hallmarks of all forms of glaucoma are damage to the optic nerve and visual field loss. New risk factors for glaucoma are always being discovered, but elevated intraocular pressure, increasing age, African-Americans and a family history of glaucoma remain among the highest risk factors.

Common types of glaucoma include:

  • Primary open angle glaucoma (POAG) - Open angle glaucoma is the most common form of glaucoma. It is generally painless and slowly progressive. It is thought to be caused by changes in the drainage tissues of the eye. Although this type of glaucoma usually involves both eyes, it can be asymmetric in severity.

  • Angle closure glaucoma - More frequent in women, angle closure glaucoma is caused by anatomical changes in the relationship between the drainage system of the eye (the angle), iris and lens. The normal drainage outflow becomes blocked and the eye pressure elevates. This form of glaucoma can occur rapidly and can be painful. It is frequently treated with a laser. The laser opens a hole in the iris, restoring a more normal ocular anatomy and aqueous flow.

  • Pigmentary glaucoma - This type of glaucoma is seen when pigment from the back of the iris deposits in the drainage tissues of the eye. This pigment causes a blockage and elevated eye pressure. It occurs more frequently in myopic (near-sighted) patients.

  • Pseudoexfoliation glaucoma - A particular material, thought to be from the lens of the eye, deposits in the drainage tissues and results in glaucoma.

  • Low tension glaucoma (LTG) - Low tension or normal tension glaucoma presents as progressive visual field loss and optic nerve damage. However, the intraocular pressure generally remains within a normal range.


Evaluation and Diagnosis

Screening for glaucoma can be done during a routine eye exam. The intraocular pressure is measured and a slit-lamp exam is performed, which is a microscopic exam of the anterior aspect of the eye. In addition, the optic nerve is examined for any evidence of abnormalities (cupping).

If the examination is suspicious for glaucoma, more specific studies can be done. These include visual field testing, optic nerve photography, and OCT (optical coherence tomography). These studies may not only help make the diagnosis of glaucoma, but help establish a baseline. Glaucoma in its most common form is a slowly progressive disease. Therefore, establishing a baseline helps assess the rate of disease progression and aid in the selection of treatment options.


Treatment Options

Treatment options for glaucoma vary widely, depending on the form and severity of glaucoma. Typically, for the most common form of glaucoma (open angle glaucoma), treatment options will include medications, laser treatments, or eye surgery. Frequently, a combination of these options may be used. The goal of glaucoma treatment is to decrease intraocular pressure and prevent damage to the optic nerve. At the beginning of treatment, the doctor will generally recommend medication or a combination of eye drops and oral medications for the specific condition.

Glaucoma is a chronic condition that is not "cured" by the treatment; it requires continued monitoring. When deciding on which treatment options, it is necessary for the physician and patient to thoroughly discuss the risks and benefits.

Medications

Several different classes of glaucoma medications are available, including beta blockers, prostaglandin analogues, alpha adrenergic agonists, miotics, oral and topical carbonic anhydrase inhibitors, and rho kinase inhibitors. These medications work by either reducing the rate at which fluid in the eye is produced or increasing the outflow of fluid from the eye.

Laser treatment can improve drainage of eye fluid and reduce intraocular pressure. Although surgery can be done to create a new passage for fluid drainage, it is usually reserved for cases that cannot be controlled by medication or if laser treatment was not successful.

Eye Drops - All eye drops may cause a burning or stinging sensation at first. This is often due to the antibacterial agent present in the drop solution, not the drug itself. While uncomfortable, it only lasts for a few seconds. It is important that you take your medication exactly as prescribed.

Since eye drops are absorbed into the bloodstream, it is important that you tell your doctor about all other medications you are taking. Some drugs can be dangerous when mixed with others. Ask your doctor or pharmacist if the medications you are taking together are safe. To minimize absorption into the bloodstream and maximize the amount of drug absorbed into the eye, close your eyes for one to two minutes after administering your drops and press lightly against the nasal corner of your eyelids to close the tear duct that drains into the nose.

Oral Medications - Sometimes, drops are not enough to control intraocular pressure. When this is the case, pills may also be prescribed. These pills also serve to lessen the production of fluid in the eye. The medication is usually taken two to four times daily. It is important to share this information with your other doctors so that they can best prescribe medications for you that will not cause potentially dangerous interactions.

Surgical Procedures

Laser surgery has become increasingly popular as an intermediate step between drugs and traditional surgery. The most common type performed for open-angle glaucoma is called trabeculoplasty. This procedure takes 10 to 20 minutes, is painless and can be performed in either a doctor's office or outpatient facility. The laser beam is focused upon the eye's drainage area. Contrary to what most people think, the laser does not burn a hole through the eye. Instead, its short bursts of energy stimulate the drain to work better.

You may go home and resume normal activities following laser surgery. Your doctor should check your intraocular pressure up to an later. After this procedure, nearly 75 percent of all patients respond well enough to be able to delay or even avoid traditional surgery. It may take a few weeks to see the full pressure-lowering effect of this procedure, during which time you may have to continue taking your medication. Some patients are eventually able to discontinue some of their medications, however this is not true in all cases. Your doctor is the best judge of determining whether or not medication is still necessary for you. Cataracts do not occur after laser surgery and complications are minimal, which are other reasons why this is a good option.

For persons with mild or moderate vision loss from glaucoma, newer minimally invasive glaucoma surgeries may be another option. Variations of these procedures generally involve enhancing drainage by bypassing the part of the drains that is clogged, either with or without a special micro device.

The most common form of traditional surgery is called a trabeculectomy. It is typically performed for moderate-to-severe cases of glaucoma. In this procedure, the surgeon creates a small trap door in the eye wall to allow the aqueous humor to drain more easily, reducing pressure in the eye. This procedure is usually done under local anesthesia, as an outpatient procedure. It is important to note that your eyes may not have their normal visual acuity for several weeks following this procedure. Although trabeculectomy is a relatively safe surgical procedure, about one-third of patients develop cataracts within five years of surgery. After trabeculectomy, most patients are able to discontinue all anti-glaucoma medications. Ten to 15 percent of patients require additional surgery.


Frequently Asked Questions

Is blindness caused by glaucoma preventable?
Regular diagnostic examinations by an ophthalmologist are important to preventing loss of vision. Ophthalmologists are medical doctors who specialize in eye care and trained to examine and treat eye diseases. Although there is no way to reverse damage, if glaucoma is diagnosed and treated early, blindness almost always is preventable.

What are the symptoms of glaucoma?
Glaucoma is called the silent thief of sight. In most cases, glaucoma has no symptoms. By the time an individual experiences decreased vision, the disease is frequently in its later stages. Since early warning signs of glaucoma are rare, it is important to have regular medical eye exams especially for those at risk.

Patients who may be at risk for glaucoma include:

  • Those over 60 (in African-Americans, the risk is present at age 40 and older)
  • A family history of glaucoma
  • Race (African-Americans and Latinos are significantly more likely to get glaucoma)
  • Certain medical conditions (diabetes, high blood pressure, heart disease)
  • Physical injuries of the eye.

The symptoms depend on the type of glaucoma the individual has. Those who have chronic glaucoma may not be aware of any symptoms because the disease develops slowly and patients rarely notice loss of peripheral vision. Those who have an acute form of glaucoma may develop severe symptoms because ocular pressure rises quickly. They may experience blurred vision, especially at night, halos or rainbows around lights, severe headaches or eye pain and nausea.

Is glaucoma painful?
Generally, the answer is no. In some forms of glaucoma, the pressure may become extremely elevated (above 40 mm high). In such cases the patient may experience pain, blurry vision, halos, or nausea and vomiting

Is there a cure for open angle glaucoma?
Unfortunately, there is no cure for glaucoma. Open angle glaucoma represents the vast majority of glaucoma that affects patients in the United States. However, there are treatments that can reduce or even halt the progression of the disease. These treatments include topical medications, laser surgery, and surgery to increase the rate of fluid drainage from the eye. Which treatment is best depends on the individual patient, as well as the type and severity of their glaucoma.

If I think the medication I'm using is causing side effects, should I stop using it for a while to see if there is an improvement? What medication should be used to treat the glaucoma during this time?
Most patients can safely suspend a medication suspected of producing unpleasant side effects for approximately one to two weeks. Your ophthalmologist may suggest that you return sooner based upon the amount of damage to your optic nerve and the level of your intraocular pressure. Depending upon the particular class of medication, it may take one to four weeks to be completely rid of the drug's effect.

What are some of the side effects of using latanoprost, travoprost, or bimatoprost?
The most common side effects of latanoprost (Xalatan) and the other medications in its class are stinging and burning related to corneal irritation, conjunctival injection (redness) and, in some patients, a darkening of the iris color. Your complaints may represent either a side effect or allergic reaction to this medication. Both of these are unlikely to disappear on their own. Latanoprost allergy or intolerance is not uncommon and may occur in as many as 5 percent of patients who are currently using other classes of antiglaucomatous medication. As always, call your doctor if you have an adverse reaction to any medication.

What are the most common side effects of eye drops used to control glaucoma?
All medications can have side effects, though not all medications cause side effects in all people. If you have side effects with one medication, it makes sense to try a different one. There are a number of different classes of medications available for treatment of glaucoma. The only way to tell if a medication is causing side effects is to stop the medication and see if they go away, then start the medication again to see if the side effects return, then repeat this process once again. Sometimes, it is the preservative in the medications rather than the medications themselves that cause the side effects. In such cases, it is possible to get preservative-free medication.

What's the best treatment for glaucoma: surgery or medication?
Quality of life is an important factor in the treatment of any chronic ailment. It is important to make a decision as to whether you want to live with significant side effects. You should first consider whether there is a way to eliminate the side effects of the medications you are taking. Talking with your ophthalmologist is the best approach to identifying possible ways to resolve the problem of medication side effects.

If you are still suffering from intolerable side effects, or if your glaucoma is uncontrolled, then surgery may be an option.

Glaucoma surgery is safer and more effective than ever. Surgery for uncomplicated open-angle glaucoma, when performed as an initial surgical procedure in a patient who has not had previous intraocular surgery, is highly effective. The chance of complications or surgical failure increases with previous intraocular surgery, complicated glaucoma, having to redo the operation for glaucoma and severe near-sightedness.

Why do some people with glaucoma and high pressure respond to as little as one eye drop while another person with a lower pressure needs to take three or four drops?
The extent or seriousness of glaucoma damage to the eye cannot not be judged by the intraocular pressure alone or the number of glaucoma medications required to control it, but rather should be defined by the amount of damage to the optic nerve and visual field. This is an important point. Glaucoma is a disease characterized by progressive injury to the nerve; this results in loss of vision that can be detected on a visual field test.

The response to glaucoma medications varies among individuals. Some individuals respond nicely to a single agent; others may require multiple medications to control their disease and prevent further vision damage. The desired intraocular pressure is chosen by the treating physician and based upon the extent of the glaucoma damage, the intraocular pressure at which the damage occurred and other factors.