The pressure of the aquious fluid that flows around the eye and optic nerve is finely balanced and the pressure keeps the eye in good shape. The space between the lens and the cornea (the clear window in the front of the eye) is filled with this clear, watery fluid and it is the production and drainage of this fluid that dicates the pressure. If the pressure raises too highly because the fluid cannot drain properly then it can result in Glaucoma.
What is Glucoma?:
The retina is the light sensitive area coating the back of the eye. Nerve cells attached to the retina send messages from the eye along the nerve fibres of the optic nerve to the brain. If the optic nerve is damaged less visual information can get to the brain.
Glaucoma is the name applied to a number of conditions where the optic nerve cells have been damaged by high pressure within the eye, or the optic nerve has been weaked somehow. If there is a low level of high pressure the sight can be lost gradually and painlessly as the optric nerve is slowly damaged. Sudden high pressure caused by injury or infection can cause sudden and often painful damage.
Although complete blindness is uncommon the damage sustained by the optic nerve is permanent, usually resulting in the loss of peripheral vision but if left untreated can effect the more sharply detailed central vision. Because damage is usually gradual, most patients are initially unaware of problems with their vision. However with early treatment sight loss can be kept to a minimum. Glaucoma affects 2% of the population in the UK.
There are four major types of Glaucoma:
- The most common form is Chronic Glaucoma which gradually causes peripheral vision impairment as eye pressure rises very slowly over months or years.
- Acute Angle Closure Glaucoma occurs when there is a sudden blockage to the fluid with in the eye. A sudden rise in eye pressure can be painful and cause permenant damage.
- Secondary Glaucoma is when another condition such as eye infection, injury to the eye or a tumor which causes a rise in pressure in the eye.
- Developmental Glaucoma (or Congenital Glaucoma) is a rare condition where babies are born with a defect in the drainage system in the eyes.
Symptoms:
The early stages of Glaucoma are difficult to detect. As the condition progresses a noticible loss in the amount of the visual field. Though central vision may be unaffecting and reading and detailed work is still good, outer vision is impaired resulting in tunnel vision. Left untreated damage to central vision can also occur. Vision may be worse in one eye than the other.
Some people with Glaucoma can have "flare ups" where inflatted eye pressure causes pain and further tempory loss of vision. Treatment with eye drops can be used to decrease the symptoms.
Causes:
Most Glaucoma is caused by the flow of aquious fluid from the eye is impaired and pressure in the eye builds up. This pressure results in damage to the optic nerve.
Primary Angle Closure Glaucoma (PACG) is where the iris (the coloured part of the eye which increases or to decreases the size of the pupil according to the brightness of the light) blocks the drainage of the fluid in the eye back into the blood stream at the angle between the iris and the cornia. PACG is where this angle is too narrow to drain sufficiently.
Primary Open Angle Glaucoma (POAG) is where the angle for drainage is open and it is unknown what is causing the pressure within the eye.
In Normal Tension Glaucoma (or Low Tension Glaucoma) the pressure in the eye is normal and it is thought that a weakness in the optic nerve or poor blood supply makes the optic nerve suceptable to damage from normal, everyday changes in eye pressure.
Secondary damage to the eyes can also cause drainage from the eye to becomne blocked.
A number of risk factors make Glaucoma more likely:
- Your chance of developing Glaucoma is greatly increased if a member of your family has suffered from it. Free NHS eye test are available for Glaucoma sufferers close family members over the age of 35.
- Glaucome gets more common with increased age, being uncommon below the age of 40.
- People of Asian decent are more succeptible from at developing some forms of Glaucoma at an earlier age and it may be more severe. The same is true of others forms amoungst people of Afro-Carbbean origin.
- Women suffer from acute and chronic Glaucoma more frequently than men.
- Short sighted people are more proan to Primary Open Angle Glaucoma.
- Long sighted people are more prone to angle closure Glaucoma.
- Diabetics are at increased risk of developing Glaucoma.
Treatment:
Treatment for Glaucoma is designed to relieve the pressure in the eye to prevent more damage. Once damage has been done it cannot be reversed but treatment can prevent or slow any further damage. Treatment is very effective and will normally retain some useful sight for the sufferer.
Different eye drops are designed for the various forms of Glaucoma and increase the outflow of fluid from the eye.
Laser eye surgery or other forms of surgery maybe needed to unblock obstructios to the outflow.
Regular visits to an optometrist is important for the sufferer and close family members.
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