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.
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.
- 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.
- 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.
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.
The same scene as viewed by a person with glaucoma.
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.
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 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.