What is Glaucoma?

Glaucoma

What is glaucoma?

Glaucoma is when the main nerve behind your eye, the optic nerve, is damaged from having too much pressure inside your eye. This causes poor eyesight.

Glaucoma affects your eyesight very gradually. Many people don't notice it at first. You may have had glaucoma for years without knowing it. The damage to your optic nerve and your eyesight is permanent, but treatment can stop it getting any worse.

Source:
Maier PC, Funk J, Schwarzer G, et al.
Treatment of ocular hypertension and open angle glaucoma: meta-analysis of randomised controlled trials.
BMJ. 2005; 331: 134.

Source:
Heijl A, Leske MC, Bengtsson B, et al.
Reduction of intraocular pressure and glaucoma progression: results from the early manifest glaucoma trial.
Archives of Ophthalmology. 2002; 120: 1268-1279.

The fluid builds up inside your eye, increasing the pressure and eventually damaging your optic nerve.

Your eye is like a small balloon filled with fluid. The fluid is watery and made by a small

gland
A gland is any group of cells in the body that makes and releases something for use by another part of the body. For example, the thyroid gland makes a hormone called thyroxine. This acts on receptors within cells. By acting on the receptors it gives the cells a message to speed up their metabolism and work harder.

gland inside your eye. Normally, extra fluid drains away through special channels. But if you have glaucoma, these special channels are blocked.

The fluid builds up inside your eye, increasing the pressure and eventually damaging your optic nerve.

Source:
Khaw PT, Shah A, Elkington AR.
ABC of eyes: glaucoma. 1: diagnosis.
BMJ. 2004; 328: 97-99.

³ Doctors call this high pressure ocular hypertension. To find out more, see High pressure inside the eye.

But you can have glaucoma even when the pressure inside your eyes is normal. This may happen if your optic nerves are more sensitive to pressure than usual. Up to 4 in 10 people with glaucoma have normal levels of pressure in their eyes.

Source:
Maier PC, Funk J, Schwarzer G, et al.
Treatment of ocular hypertension and open angle glaucoma: meta-analysis of randomised controlled trials.
BMJ. 2005; 331: 134.

¹ This kind of glaucoma is called normal-tension glaucoma.

We don't know for sure what causes glaucoma. But we know you're more likely to get glaucoma if:

The pressure inside one or both of your eyes is very high. You need some pressure to keep your eyeball in its correct shape. But too much pressure can damage your optic nerve and your eyesight. About 1 in 10 people over 40 have high pressure inside their eyes, although not all of them get glaucoma.

Source:
Alward WLM.
Medical management of glaucoma.
New England Journal of Medicine. 1998; 339: 1298-1307.

⁴ Your eye doctor (optician) can measure the pressure inside your eyes with a simple test.
Someone in your family has glaucoma.

Source:
Alward WLM.
Medical management of glaucoma.
New England Journal of Medicine. 1998; 339: 1298-1307.

⁴
You have a black African heritage.

Source:
Leske MC, Connell AM, Wu SY, et al.
Incidence of open angle glaucoma: the Barbados eye studies.
Archives of Ophthalmology. 2001; 119: 89-95.

⁵
You are over 40. The chances of getting glaucoma increase with age. About 1 or 2 in 100 people over age 40, and 5 in 100 people over age 70, have glaucoma.

Source:
Shah R, Wormald R.
Glaucoma.
Clinical Evidence 2006; 15: 1-2.

⁶
You have

diabetes
Diabetes is a condition that causes too much sugar to circulate in your blood. It happens when your body stops making a hormone called insulin (type 1 diabetes) or when insulin stops working (type 2 diabetes).

diabetes,

high blood pressure
Your blood pressure is considered to be high when it is above the accepted normal range. The usual limit for normal blood pressure is 140/90. If either the first (systolic) number is above 140 or the lower (diastolic) number is above 90, a person is considered to have high blood pressure. Doctors sometimes call high blood pressure "hypertension."

high blood pressure or have taken

steroids
Steroids are a type of chemical. Your body naturally produces steroids, which play a part in many of its processes. For example, steroids are involved in how your immune system, reproductive system and metabolism work. Steroids can also be given as medicines and are used for a number of different conditions: including asthma, rheumatoid arthritis and eczema. Corticosteroids are not the same as the steroids used by some body builders and athletes. Those steroids are called 'anabolic steroids'.

steroids for a long time.

Source:
Beers MH, Berkow R (editors).
The Merck manual of diagnosis and therapy.
17th edition. Wiley, Whitehouse Station, NJ, U.S.A.; 1999.

⁷

Sources for the information on this page:

Maier PC, Funk J, Schwarzer G, et al.Treatment of ocular hypertension and open angle glaucoma: meta-analysis of randomised controlled trials.BMJ. 2005; 331: 134.

Heijl A, Leske MC, Bengtsson B, et al.Reduction of intraocular pressure and glaucoma progression: results from the early manifest glaucoma trial.Archives of Ophthalmology. 2002; 120: 1268-1279.

Khaw PT, Shah A, Elkington AR.ABC of eyes: glaucoma. 1: diagnosis.BMJ. 2004; 328: 97-99.

Alward WLM.Medical management of glaucoma.New England Journal of Medicine. 1998; 339: 1298-1307.

Leske MC, Connell AM, Wu SY, et al.Incidence of open angle glaucoma: the Barbados eye studies.Archives of Ophthalmology. 2001; 119: 89-95.

Shah R, Wormald R.Glaucoma.Clinical Evidence 2006; 15: 1-2.

Beers MH, Berkow R (editors).The Merck manual of diagnosis and therapy.17th edition. Wiley, Whitehouse Station, NJ, U.S.A.; 1999.

This information was last updated on Jul 29, 2008

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment.
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