What is Glaucoma?

The optic nerve of the eye carries images to the brain. Glaucoma is a condition in which the optic nerve becomes damaged. The optic nerve is like a telephone cable containing about 1.2 million nerve fibres, or "wires" within the cable. Glaucoma damages nerve fibres, causing blind spots to develop.

Back to Top ^

What Causes Glaucoma?

Many people know that glaucoma has something to do with pressure inside the eye -- the intraocular pressure. Pressure builds up in the eye when the clear liquid inside the eye called the aqueous humor is prevented from draining properly. The resulting increase in pressure within the eye can damage the optic nerve.

Aqueous humor fluid (red arrow) flows forward through the pupil and out through the trabecular meshwork and into Schlemm's canal in the eye wall to be absorbed within the episclera and conjunctiva.

There is a transparent liquid, the aqueous humor fluid, that circulates inside the eye. It supplies nutrients to the eye and removes metabolic waste products. A small amount of this fluid is produced constantly, and an equal amount flows out of the eye through a microscopic drainage system. (This fluid is not part of the tears on the outer surface of the eye.) The aqueous fluid normally flows forward through the pupil and into the anterior chamber in the front section of the eye. Then it empties into a drain in the front of the eye called the trabecular meshwork. The trabecular meshwork is located inside the eye at the junction of the clear cornea and the white sclera. You can think of the flow of aqueous fluid as a sink with the faucet turned on all the time. If the drainpipe gets clogged, water collects in the sink and the sink may overflow. Because the eye is a closed structure, the excess fluid cannot over-flow if the drain is clogged. If the trabecular meshwork is blocked, the fluid pressure within the inner eye increases, which can damage the optic nerve and lead to vision loss.

Aqueous humor fluid (red arrow) cannot drain properly though the trabecualr meshwork.

Progressive glaucomatous cupping of the optic nerve. The central white cup of the optic nerve becomes enlarged as the rim of the nerve becomes progressively thinner. (Black Arrow)

Ophthalmologists used to think that high intraocular pressure was the main cause of optic nerve damage in glaucoma, however we now know that even people with "normal" pressure can experience vision loss from glaucoma.

Some people with elevated pressure never develop the optic nerve damage of glaucoma. These people still need to be followed carefully by an ophthalmologist, because they are considered "glaucoma suspects."

There may be other factors which affect the optic nerve, even when pressure is in the "normal" range. Elevated pressure is still considered the major risk factor for glaucoma, though, because studies have shown that the higher the pressure is, the more likely optic nerve damage is to occur.

Navigation is difficult

Most people who have glaucoma don't notice any symptoms. As optic nerve fibres are damaged by glaucoma, small blind spots may begin to develop, usually in the side -- or peripheral -- vision. The top photo at left shows how a scene would be viewed by a person with normal vision. The image to its right shows the same scene as viewed by a person with advanced glaucoma. Many people don't notice the blind spots until significant optic nerve damage has already occurred. If the entire nerve is destroyed, blindness results.

These photos demonstrate how central reading vision is preserved in glaucoma. The left image depicts a person with normal vision viewing a table surface. The right image represents the same table surface as viewed by a person with advanced vision loss from glaucoma. The bottom image depicts reading vision preserved despite peripheral vision loss. If glaucoma is not sufficiently controlled however, then reading vision will also be lost eventually.

Central vision is preserved until late in the disease process Reading is preserved until late in the disease

Back to Top ^

Higher Risk of Glaucoma Among African Americans

Primary open-angle glaucoma is the leading cause of blindness among African-Americans. It occurs six to eight times more often among African-Americans than Caucasians, and often begins at a younger age. Studies show that African-Americans between ages 45 and 65 are 14-17 times more likely to lose vision from glaucoma than Caucasians with glaucoma in the same age group.

The reason for the higher rate of glaucoma and subsequent blindness among African-Americans is still uncertain. Everyone can protect themselves against vision loss from glaucoma by being aware of their risk level for developing the disease, and by having regular eye examinations for glaucoma at appropriate intervals.

Back to Top ^

Types of Glaucoma

The most common form of glaucoma is open-angle glaucoma. It occurs with aging. The drain of the eye, or trabecular meshwork, becomes less efficient with time, and pressure within the eye gradually increases. If this increased pressure damages the optic nerve, it is called glaucoma. Over 90% of adult glaucoma patients have this type of glaucoma.

Chronic open-angle glaucoma damages vision gradually and painlessly. Most people who develop open-angle glaucoma notice no symptoms until very late in the disease process when vision becomes impaired.

Angle-closure glaucoma is the other major type of glaucoma. In angle-closure glaucoma, aqueous fluid cannot circulate through the pupil and trabecular meshwork adequately. This condition can occur gradually or suddenly.

Aqueous humor fluid (red arrow) cannot flow through the pupil and is blocked by the iris.

When acute angle-closure glaucoma occurs suddenly, it is considered an emergency because optic nerve damage and subsequent vision loss can occur within hours of the onset of the problem. Symptoms from this kind of glaucoma can include headache, nausea and vomiting, blurred vision, seeing haloes around light, and pain in the eye. Unless treated quickly, blindness can result.

Chronic angle-closure glaucoma, like open-angle glaucoma, may cause vision damage without symptoms. Although angle-closure glaucoma is unusual, people of Asian or Eskimo ancestry are at higher risk of developing it. As with other forms of glaucoma, age and family history are also risk factors, and the problem seems to occur in older women more often than men or younger people.

Sometimes glaucoma occurs secondary to another eye condition. A secondary condition can be traced to another cause, such as previous injury or illness.

"Normal (or low) pressure" glaucoma is an unusual and less understood form of the disease. In this type of glaucoma, the optic nerve is damaged even though the patient's intraocular pressure is consistently normal.

Childhood glaucoma is rare, and starts in infancy, childhood or adolescence. Like open-angle glaucoma, there are few, if any, symptoms in the early stage, and blindness can result if it is left untreated. Like most types of glaucoma, this type of glaucoma is thought to have a hereditary component.

Congenital glaucoma is a type of childhood glaucoma that usually appears soon after birth, although it can become apparent later in the first year of life. Unlike other childhood glaucoma's, congenital glaucoma often has noticeable signs, including tearing, light sensitivity, and cloudiness of the cornea. This type of glaucoma is more common in boys, and can affect one or both eyes.

Back to Top ^

How is Glaucoma Detected?

Regular eye examinations by your ophthalmologist are the best way to detect glaucoma. Because your ophthalmologist is a medical doctor, he or she can detect and treat glaucoma.

Doctors used to think that one simple test, measuring the eye's intraocular pressure, was enough to diagnose glaucoma. But recent studies show that just measuring eye pressure is not a reliable way to detect glaucoma. Eye pressure can fluctuate at different times during the day. Also, some people's optic nerves are not damaged by high pressure while others' optic nerves are damaged by relatively low pressure. To be safe and accurate, four factors should be checked before making a glaucoma diagnosis:

1. the eye pressure (intraocular pressure or IOP)
2. the shape and colour of the optic nerve
3. the field of vision
4. the angle in the eye where the iris meets the cornea

During your complete and painless eye examination, your ophthalmologist will:

Obtain your medical history. The doctor or staff will ask questions about your medical and personal history, as well as your family's medical history.

Tonometry-measurement of intraocular pressure Measure your intraocular pressure using an instrument called a tonometer. The tonometer measures pressure using a pressure-sensitive tip placed gently near or against the eye. Short-acting anaesthetic drops are used to numb the eye for this procedure. Normal pressures usually range from 12-21 mmHg.

Gonioscopy: examination of the drainage angle of the eye Inspect the drainage angle of your eye. The ophthalmologist places a special magnifying lens painlessly on the eye to examine the drainage area between the iris and the cornea to see if it is blocked. This procedure is called gonioscopy. It helps the doctor determine whether open- or closed-angle glaucoma is present.

One method of ophthalmoscopy: examination of the optic nerve Perform ophthalmoscopy. The ophthalmologist uses drops to dilate (or widen) the pupil so he or she may look at the optic nerve using a special instrument to closely examine the shape and colour of the optic nerve. A nerve that is "cupped" or not a healthy pink colour is cause for concern. This allows the ophthalmologist to evaluate any optic nerve damage that may have occurred. Special stereoscopic colour photographs of your optic nerves may be taken.

Computerized automated perimetry: examination of peripheral vision Perform perimetry to test your field of vision. This represents your peripheral vision, or side vision. This test can tell the ophthalmologist how much vision has been lost, even if you notice no impairment. Patients look straight ahead into a white, bowl-shaped instrument, and an ophthalmic technician moves different sized points of light to various places around the bowl-shaped area. Patients are asked to indicate—by the push of a button—as soon as they think they see the light, even though the light may be very dim.

Back to Top ^

Heidelberg Retinal Tomograph

In glaucoma, pressure within the eye causes damage to the optic nerve that can eventually lead to significant visual loss if unrecognized or untreated. For that reason, careful monitoring of the appearance of the optic nerve head has always been an important aspect of screening and treating patients with glaucoma. The Heidelberg Retinal Tomograph (HRT) is a scanning laser system that allows ophthalmologists to objectively monitor changes in the contour of the optic nerve head over time. It is the newest advance in the armamentarium to identify early glaucoma and monitor progression of the disease. University Eye Specialists are the first physicians to acquire and use this technology.

The HRT is a simple test that takes minutes and can be performed in the office. A scanning laser is used to "map" the contour and appearance of the optic nerve. The scanning laser is totally safe for the eye and provides important information about the appearance of the optic nerve. The data produced by the HRT compares your optic nerve characteristics to standard measures of the population. This may help diagnose glaucoma earlier than previously thought possible. Even more importantly, the HRT provides the ability to detect subtle changes in the contour and appearance of your optic nerve over a long period of time. This reduces some of the subjectivity of visual observation and in some instances can more accurately indicate progression of glaucomatous eye injury.

Some of these tests may not be necessary for every patient, but more tests may be added, or repeated more frequently if glaucoma is suspected or if glaucoma damage increases over time.

Because your eyes may be dilated during your exam, you may want to bring sunglasses with you to your appointment. Dilation can make your eyes extra blurred and sensitive to light for a few hours after your exam.

Back to Top ^

Who is at Risk for Glaucoma?

High pressure alone does not necessarily mean that you have glaucoma. Your ophthalmologist may tell you that you're a glaucoma suspect if you have one or more risk factors for glaucoma. These most important risk factors for glaucoma are elevated intraocular pressure, family history of glaucoma, African heritage, older age, optic nerve appearance, and past injuries to the eye. Your ophthalmologist will analyse all of these factors before deciding whether you need treatment for glaucoma, or whether it is safe to monitor you closely as a glaucoma suspect. Being considered a glaucoma suspect means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect the early signs of damage to the optic nerve.

Elevated eye pressure is sometimes called "ocular hypertension." This means that your pressure is higher than what is considered "normal." A diagnosis of ocular hypertension does not mean you have glaucoma, but it does mean you're at increased risk to develop optic nerve damage, and should have more frequent medical eye examinations. Sometimes your ophthalmologist will recommend medication to lower your pressure.

Back to Top ^

How is Glaucoma Treated?

As a rule, optic nerve and vision damage caused by glaucoma cannot be reversed. Treatment for glaucoma may include medication and/or surgery to prevent or slow further damage to your eye from happening. Because glaucoma can worsen over time without you being aware of it, it is important for you to follow up with your doctor as prescribed. Your treatment may need to be changed over time. Once diagnosed, it requires constant, lifelong care. Continual observation and treatment can control the intraocular pressure, which protects the nerve and prevents vision loss.

Many people think that glaucoma has been cured when high eye pressures have been brought down to safe levels with medication or surgery. In fact, the glaucoma is only being controlled. It has not been cured. Regular check-ups including repeat visual field and optic nerve examinations are necessary even after medications or surgery have successfully controlled the eye pressures.

Back to Top ^

Medications for Glaucoma

There is no "cure" for glaucoma, but it can be treated and controlled. Even when treatment is effective, people with glaucoma need to have their eyes checked regularly, and often need to continue treatment for the rest of their lives. This may seem like a burden, but is preferable to losing sight.

Treatment for glaucoma focuses on lowering intraocular pressure to a level the ophthalmologist thinks is unlikely to cause further optic nerve damage. This level is sometimes known as the "target pressure." High pressure may damage your optic nerve, which can lead to vision loss. That level differs from individual to individual, and one person's "target pressure" may change during the course of his or her lifetime.

Treatment of glaucoma involves decreasing the eye pressure, either by slowing the production of aqueous fluid within the eye, or by improving the flow through the trabecular meshwork drain.

Back to Top ^

Types of Medications

If you have glaucoma your ophthalmologist will usually first prescribe medication to lower your intraocular pressure. Doctors try to use the least amount of medication that produces the best results with the fewest side effects. Medications usually must be taken regularly from two to four times a day, every day. Remembering to take prescribed medication every day is a scheduling chore that is absolutely necessary to control eye pressures.

Medications may be topical, such as eye drops, inserts (wafer-like strips of education you put in the corner of your eye) or eye ointments. Some other glaucoma medications are prescribed to be taken by mouth as pills or tablets. Topical medications reduce or control pressure in one of two ways: they open the drain of the eye so aqueous humor fluid can flow more easily, or they reduce the amount of fluid produced by the eye in the first place.

Back to Top ^

Possible Medication Side Effects

Any medication, including eye drops, may have side effects. Some people taking glaucoma medication may experience:

• Stinging or redness of eyes
• Blurred vision
• Headache
• Changes in pulse, heartbeat, or breathing
• Changes in sexual desire
• Mood changes
• Tingling of fingers and toes
• Drowsiness
• Loss of appetite
• Change of iris colour (in people with light coloured eyes taking prostaglandin analogs)
• Dry mouth

Most side effects aren't serious, and often disappear after a while. Not every patient will experience side effects with glaucoma medication. Since it is very important that people with glaucoma carefully follow their ophthalmologists' recommended treatments, any side effects of medication should be discussed with the doctor. You and your ophthalmologist may decide to change medications or type of treatment.

Back to Top ^

Surgery For Glaucoma

For some people, surgery might be recommended treatment for glaucoma. Your ophthalmologist may suggest surgery as a first treatment, or after trying medication to lower your pressure.

There are several different types of surgery for glaucoma. The kind of surgery you and your ophthalmologist decide is right for you depends on many factors, including the type and severity of your glaucoma, and other eye problems or health conditions.

Glaucoma surgery may be performed using a laser (a concentrated beam of light) or conventional surgical instruments.

Back to Top ^

Laser Surgery

Trabeculoplasty is used to treat open-angle glaucoma. In trabeculoplasty, a laser is used to place "spot welds" in the drainage area of the eye-- also known as the trabecular meshwork -- that allow the aqueous to drain more freely. This procedure uses topical anaesthetic eye drops so that the surgery is painless.

A small hole (iridotomy) is made in the iris (arrow)

Iridotomy is another kind of laser surgery used to treat angle-closure glaucoma. In this procedure, the surgeon uses the laser to make a small hole in the iris-- the coloured part of the eye -- which allows the aqueous to flow more freely to the drain of the eye (trabecular meshwork). This procedure uses topical anaesthetic eye drops so that the surgery is painless.

Laser procedures for glaucoma are performed in our office. Little recuperation is needed after laser eye surgery. Patients may experience some local eye irritation and mildly blurred vision, but can usually resume their normal activities the same day of surgery.

For some patients, laser surgery is not chosen as treatment for glaucoma. Sometimes, when vision loss is rapid, or medication fails to lower pressure sufficiently, "conventional" incisional surgery is the best option.

Back to Top ^

Incisional Surgery

Two examples of the postoperative appearance of a "bleb" after glaucoma filtration surgery (arrows)

Glaucoma filtering surgery is performed in a hospital or outpatient surgery centre, with local anaesthesia, and gentle sedation. The surgeon uses very delicate instruments to remove a tiny piece of the wall of the eye (the sclera), leaving a tiny opening. The aqueous fluid can then drain through this opening, thereby reducing the intraocular pressure. The fluid is reabsorbed into the bloodstream.

A small plastic tube drains aqueous humor fluid from the front of the eye.

In some patients, the surgeon may place a small plastic tube or valve in the eye through a tiny incision in the sclera. The valve acts a regulator for the build-up of aqueous fluid within the eye. When the intraocular pressure reaches a certain level, the valve opens, allowing the fluid to flow out of the eye's interior, where it can be reabsorbed by the body. The procedure may take place in the hospital operating room or outpatient surgical centre, and can be done under local anaesthesia.

The recuperative period following incisional glaucoma surgery is usually short. You may need to wear an eye patch for a few days after surgery, and avoid activities which expose the eye to water, such as showering or swimming. The ophthalmologist may recommend you refrain from heavy exercise, straining or driving for a short time after surgery, to avoid complications. Sometimes vision is blurred for a period of time after surgery.

Back to Top ^

Possible Complications

As with any type of surgery, there are risks associated with glaucoma surgery. Fortunately, complications are unusual. Important risks of eye surgery include infection, bleeding, and vision loss.

Sometimes one surgical procedure is not effective in halting the progress of glaucoma. In these cases, repeat surgery, and/or continued treatment with topical or oral medications may be necessary.

Your age, eye structure, type of glaucoma, and other medical conditions are all considerations when deciding how to treat your glaucoma.

The ophthalmologist, in partnership with the patient, is best able to make the appropriate treatment decisions.

The American Academy of Ophthalmology recommends that African-Americans ages 20-39 without symptoms for glaucoma have a comprehensive eye examination every 3-5 years; and African-Americans over 40 have their eyes examined through dilated pupils at least every two years.

Everyone should have regular medical eye examinations, but those at risk for glaucoma need to have more frequent exams.

The American Academy of Ophthalmology recommends you have an examination:

• Every 3 to 5 years if you are age 39 or over
• Every 1 to 2 years if you are age 50 or over
• if a family member has glaucoma
• if you are of African ancestry
• if you have had a serious eye injury in the past
• if you are taking steroid medication

Remember that early detection and treatment can prevent vision damage.

Here is another site you may find useful and helpful to learn more about glaucoma: