Glaucoma is the name given to a group of conditions which result in damage to the optic nerve, with a resulting reduction in vision. Intraocular pressure inside the eye is often the cause of this damage. Known as the 'silent thief of sight', glaucoma damages sight so gradually that it is often only detected when it is in an advanced stage. It is estimated that 65 million people worldwide suffer from glaucoma. Early diagnosis is crucial to minimize or prevent this nerve damage, with the resulting loss of vision.
Doctors understand that damage to the optic nerve is caused by intraocular pressure, but they do not yet fully understand why that pressure is associated with damage to the optic nerve, a main characteristic of glaucoma. Research is still underway to find out how to prevent or stop this deterioration in retinal ganglion cells. The pressure comes from the fluid, called aqueous humor, which is normally produced in the front of your eye. Aqueous humor normally drains away through a small drainage system between the iris and the cornea. When this drainage fails to function properly, the aqueous humor builds up and pressure builds within the eye.
There are different types of glaucoma. Primary open-angle glaucoma is caused by the drainage between the iris and the cornea being clear, but the drainage channels in the angle being partially obstructed. These channels are called the trabecular meshwork. The cause of this glaucoma remains unknown, but the consequences are serious. If the aqueous fluid fails to drain away; it builds up and causes an increase in pressure on the eye which in turns damages the optic nerve. This damage is painless and slow. Unfortunately the first warning a person has is the gradual loss of sight.
Closed-angle glaucoma occurs when the drainage angle is blocked or decreased by a bulge in the iris. Once again the aqueous humor cannot drain, pressure builds and damage is caused to the optic nerve. This type of glaucoma may occur gradually, and is called chronic angle-closure glaucoma. It may also occur suddenly and is then known as acute angle-closure glaucoma. Often this type of glaucoma develops in people who had a narrow drainage angle anyway. Acute angle-closure glaucoma may be triggered by a sudden dilation of the pupil as it reacts to darkness, stress, excitement or medications. Antihistamines and some antidepressants are known to cause this dilation. Eyedrops which are used in an eye exam also dilate the pupils to enable a thorough check to be carried out.
Pigmentary Glaucoma takes its name from its association with the dispersal of pigment granules in the eye. This type of glaucoma generally develops in young and middle-aged adults. When these pigment granules accumulate in the trabecular meshwork, once again the aqueous fluid build up, causes pressure and results in damage to the optic nerve. Some physical activities such as running may be the cause of these pigments being disturbed. The good news is that this type of glaucoma can be diagnosed early on, during an eye exam by a qualified ophthalmologist.
The following factors may indicate an increased risk of glaucoma developing:
- Increased intraocular pressure. If your eye pressure if higher than it should be, you may be at risk of developing glaucoma
- Age. Unfortunately age increases the risk, particularly in the over 60s.
- Ethnicity. African-Americans and Mexican-Americans are shown to have a 6-8 times higher chance of developing glaucoma. These high-risk groups should have their eye pressure monitored before the age of 30.
- Family history. There may be a genetic link which can be inherited.
- Medical conditions such as diabetes and high blood pressure increase the risk of glaucoma.
- Eye injury or certain treatments can trigger glaucoma.
- Nearsightedness. Those who are naturally near-sighted are at increased risk.
- Corticosteroid use, for example in eyedrops over a prolonged period, are also known to increase the risk of glaucoma.
The good news is that regular eye checks can help detect glaucoma in its early stages, particularly if you have one or more of the above factors which increase the risk.
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