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The eye, like many parts of the body, is full of fluid. This fluid is important for the functioning and health of the eye. In the posterior chamber it is thick and jelly like and is called the vitreous humor. The vitreous provides support for the retina to prevent a retinal detachment. In the anterior chamber it is called the aqueous humor. The aqueous is thinner and more watery than the vitreous, and is a transport system to provide all the nutrients that the lens needs to stay healthy. The aqueous is formed in glands, circulates around the lens and then drains away through the canal of Schlem in front of the iris. If the drainage channel becomes blocked the pressure in the fluid will start to rise. This increased pressure damages the nerves in the eye leading to a loss of vision. This increased pressure and loss of vision is GLAUCOMA.

Glaucoma usually develops slowly and painlessly. The vision loss is not sudden and is at the edge of the visual field, the area of the vision where you would say that you notice something out of "the corner of your eye." This means that people often do not know that it is happening to them.

Glaucoma is the biggest preventable cause of blindness in Europe and North America. Fortunately it is preventable but it needs to be detected and treated early in its course. The detection is based on three measurements, the appearance of the optic nerve, a measurement of the pressure and a measurement of the sensitivity of the peripheral vision, a fields test. These tests are easy and painless to conduct and are routinely carried out by optometrists during an eye examination.

Glaucoma affects about 2% of people over the age of 40. Over the age of 70 it becomes even more common. You are more likely to suffer from glaucoma if an immediate relative already has glaucoma, for instance parents or brothers or sisters, and anyone who does should have an annual screening test which is paid for by the NHS.

Treatment is very effective if started soon enough. It acts in two ways, to reduce the production of the fluid and to increase the drainage. Beta blocking drops such as Timoptol, Betagan, Teoptic and Betoptic reduce the production of fluid while pilocarpine and carbachol drops increase the escape of fluid from the eye.

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