Abnormally high pressure of the fluid inside the eye
- Rare under the age of 40; more common over the age of 60
- Some types run in families
- Gender and lifestyle are not significant factors
Fluid continually moves into and out of the eye to nourish its tissues and maintain its shape. In glaucoma, the flow of fluid out of the eye becomes blocked and pressure rises inside the eye. This high pressure may permanently damage nerve fibres in the light-sensitive retina and in the optic nerve, which carries nerve signals from the retina to the brain. Glaucoma becomes more common with age, and mainly affects people over the age of 60. If untreated, the condition may cause blindness.
What are the types?
There are two common types of glaucoma (acute and chronic) and two rarer types (secondary and congenital). Acute glaucoma develops suddenly, causing rapid loss of vision and severe eye pain. In contrast, chronic glaucoma develops slowly and painlessly, often over many years. It may not cause noticeable symptoms until the eyes are badly damaged. Both types can run in families.
Secondary glaucoma occurs as a result of an underlying eye disorder, such as retinal vein occlusion or uveitis, or from using certain drugs, such as corticosteroid eyedrops (see Drugs acting on the eye). Secondary glaucoma can result in blindness. Congenital glaucoma is due to a defect in the drainage apparatus of the eye. It is present from birth and can also result in blindness (see Congenital blindness).
Glaucoma is diagnosed by measuring pressure in the eye using an instrument called a tonometer (see Tonometry). Treatment should always be given immediately. Eyedrops are used first to reduce pressure in the eye (see Drugs for glaucoma). In some cases, surgery is necessary to increase drainage of fluid and prevent build-up of pressure in the eye (see Laser iridotomy, and Trabeculectomy). Correct treatment normally minimizes further vision loss.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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