Facts About Glaucoma

This information was developed to help patients and their families search for general information about glaucoma. An eye care professional who has examined the patient’s eyes and is familiar with his or her medical history is the best person to answer specific questions.

Glaucoma Defined

What is Glaucoma?

Glaucoma is a group of diseases that damage the eye’s optic nerve and can result in vision loss and blindness. However, with early detection and treatment, you can often protect your eyes against serious damage.

The optic nerve

The optic nerve is a bundle of more than 1 million nerve fibres. It connects the retina to the brain. (See diagram above.) The retina is the light-sensitive tissue at the back of the eye. A healthy optic nerve is necessary for good vision.

How does the optic nerve get damaged by open-angle glaucoma?

Several large studies have shown that eye pressure is a major risk factor for optic nerve damage. At the front of the eye is a space called the anterior chamber. A clear fluid flows continuously in and out of the chamber and nourishes nearby tissues. The fluid leaves the chamber at the open angle where the cornea and iris meet. (See diagram below.) When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.

In open-angle glaucoma, even though the drainage angle is “open”, the fluid passes too slowly through the meshwork drain. Since the fluid builds up, the pressure inside the eye rises to a level that may damage the optic nerve. When the optic nerve is damaged from increased pressure, open-angle glaucoma and vision loss may result. That’s why controlling pressure inside the eye is important.

Another risk factor for optic nerve damage relates to blood pressure. Thus, it is important to also make sure that your blood pressure is at a proper level for your body by working with your medical doctor.

Fluid pathway is shown in teal.

Can I develop glaucoma if I have increased eye pressure?

Not necessarily. Not every person with increased eye pressure will develop glaucoma. Some people can tolerate higher levels of eye pressure better than others. Also, a certain level of eye pressure may be high for one person but normal for another.

Whether you develop glaucoma depends on the level of pressure your optic nerve can tolerate without being damaged. This level is different for each person. That’s why a detailed eye exam is very important. It can help your optometrist determine what level of eye pressure is normal for you.

Can I develop glaucoma without an increase in my eye pressure?

Yes. Glaucoma can develop without increased eye pressure. This form of glaucoma is called low-tension or normal-tension glaucoma. It is a type of open-angle glaucoma.

Who is at risk for open-angle glaucoma?

Anyone can develop glaucoma. Some people, listed below,  are at higher risk than others:

• Raised intraocular pressure.
• Myopia.
• Diabetes.
• Positive family history: incidence increases x 2-4 for those with an affected sibling.
• Ethnicity: some ethnic groups have increased incidence of glaucoma. People of East Asian and Inuit ethnicity have an increased risk of closed angle glaucoma but a low incidence of open angle glaucoma. People of African descent are three times more likely to develop open-angle glaucoma.
• Gender: women are three times more likely than men to develop angle-closure glaucoma due to their shallow anterior chambers.
• Prolonged use of steroids.
• Conditions which severely restrict blood flow to the eye – eg, diabetic retinopathy, central retinal vein occlusion.
• Eye trauma.
• Uveitis.
• Systemic hypertension.

A comprehensive eye exam can reveal more risk factors, such as high eye pressure and abnormal optic nerve anatomy. Anyone suspected of having glaucoma, following an eye examination, is referred to an eye specialist or ophthalmologist who is then able to assess the patient more thoroughly. In some people with certain combinations of these high-risk factors, medicines in the form of eye drops reduce the risk of developing glaucoma by about half.

Glaucoma Symptoms

At first, open-angle glaucoma has no symptoms. It causes no pain. Vision stays normal. Glaucoma can develop in one or both eyes.

Without treatment, people with glaucoma will slowly lose their peripheral (side) vision. As glaucoma remains untreated, people may miss objects to the side and out of the corner of their eye. They seem to be looking through a tunnel. Over time, straight-ahead (central) vision may decrease until no vision remains.

How is glaucoma detected?

Glaucoma is detected through a comprehensive eye exam that includes the following:

Visual acuity test. This eye test chart measures how well you see at various distances.

Visual field test. This test measures your central and peripheral (side vision). It helps the optometrist determine if you have lost peripheral vision, a sign of glaucoma.

Tonometry is the measurement of pressure inside the eye by using an instrument called a tonometer. The instrument emits a harmless and painless ‘puff’ of air on to the eye, allowing the pressure to be noted.

Can glaucoma be cured?

No. There is no cure for glaucoma. Vision lost from the disease cannot be restored, but it can be managed and further visual loss can be prevented.

Glaucoma Treatments

Immediate treatment for early-stage, open-angle glaucoma can delay progression of the disease. That’s why early diagnosis is very important.

Glaucoma treatments include medicines, laser trabeculoplasty, laser iridotomy, cyclodiode laser treatment or a combination of any of these. While these treatments may save remaining vision, they do not improve sight already lost from glaucoma.

Medicines. Medicines in the form of eye drops, are the most common early treatment for glaucoma. Taken regularly, these eye drops lower eye pressure. Some medicines cause the eye to make less fluid. Others lower pressure by helping fluid drain from the eye.

Glaucoma medicines need to be taken regularly as directed by your ophthalmologist. Most people have no problems. However, some medicines can cause headaches or other side effects. For example, drops may cause stinging, burning, and redness in the eyes.

Any side effects from taking the medication, should be reported to your ophthalmologist.

Because glaucoma often has no symptoms, people may be tempted to stop taking or may forget to take their medicine. You need to use the drops or pills as long as they help control your eye pressure. Regular use is very important.

A tonometer measures pressure inside the eye to detect glaucoma.

Laser trabeculoplasty: a laser is used to open up the drainage tubes within the eye, which allows more fluid to drain out of the eye and reduces the pressure inside it.

Laser iridotomy: a laser is used to create holes in the iris (coloured part of the eye) to allow fluid to drain from the eye.

Cyclodiode laser treatment: a laser is used to destroy some of the tissue in the eye that produces aqueous humour (the liquid inside the eye), which can reduce pressure in the eye.

Surgery

Surgery may be recommended as an alternative to laser treatment in some cases. Types of surgery include:

trabeculectomy – the most common type of operation, it involves removing part of the eye drainage tubes to allow fluid to drain more easily.

trabeculotomy – similar to trabeculectomy, but an electric current is used to remove a small part of the eye drainage tubes.

viscocanalostomy – an operation to remove part of the sclera ( the white of the eyeball), so fluid can drain from the eye more easily.

What are some other forms of glaucoma and how are they treated?

Open-angle glaucoma is the most common form. Some people have other types of the disease.

In low-tension or normal-tension glaucoma, optic nerve damage and narrowed side vision occur in people with normal eye pressure. Lowering eye pressure at least 30 percent through medicines slows the disease in some people. Glaucoma may worsen in others despite low pressures.

A comprehensive medical history is important to identify other potential risk factors, such as low blood pressure, that contribute to low-tension glaucoma. If no risk factors are identified, the treatment options for low-tension glaucoma are the same as for open-angle glaucoma.

In angle-closure glaucoma, the fluid at the front of the eye cannot drain through the angle and leave the eye. The angle gets blocked by part of the iris. People with this type of glaucoma may have a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. If you have these symptoms, you need to seek treatment immediately. This is a medical emergency. If your doctor or optometrist is unavailable, go to the nearest hospital or clinic. Without treatment to restore the flow of fluid, the eye can become blind. Usually, prompt laser surgery and medicines can clear the blockage, lower eye pressure, and protect vision.

In congenital glaucoma, children are born with a defect in the angle of the eye that slows the normal drainage of fluid. These children usually have obvious symptoms, such as cloudy eyes, sensitivity to light, and excessive tearing. Conventional surgery typically is the suggested treatment, because medicines are not effective and can cause more serious side effects in infants and be difficult to administer. Surgery is safe and effective. If surgery is done promptly, these children usually have an excellent chance of having good vision.

Conventional surgery makes a new opening for the fluid to leave the eye.

Secondary glaucomas can develop as complications of other medical conditions. For example, a severe form of glaucoma is called neovascular glaucoma, and can be a result from poorly controlled diabetes or high blood pressure. Other types of glaucoma sometimes occur with cataract, certain eye tumours, or when the eye is inflamed or irritated by a condition called uveitis. Sometimes glaucoma develops after other eye surgeries or serious eye injuries. Steroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in some people. There are two eye conditions known to cause secondary forms of glaucoma.

Pigmentary glaucoma occurs when pigment from the iris sheds off and blocks the meshwork, slowing fluid drainage.

Pseudoexfoliation glaucoma occurs when extra material is produced and shed off internal eye structures and blocks the meshwork, again slowing fluid drainage.

Depending on the cause of these secondary glaucomas, treatment may include medicines, laser surgery, or conventional surgery.

Loss of Vision

If you have lost some sight from glaucoma, ask your eye care professional about low vision services and devices that may help you make the most of your remaining vision.