Eye - Glaucoma
The name Glaucoma is for a group of eye diseases this is when the optic nerve is damaged. In the most worst cases, the damage to the eye nerves can lead to blindness, if glaucoma is detected and treated early this can be avoided.
A common type of glaucoma is called open angle glaucoma (or chronic simple glaucoma), this condition on average affects around 20 in every 1000 hundred people over the age of 40, this increases with increasing age.
A healthly normal eye
The eyeball is filled with a watery fluid called aqueous humour, which creates pressure and helps maintain the shape of the eyeball (see the diagram, below).
The aqueous humour that fills the anterior chamber (front part of the eye) is produced by the ciliary body, just behind the iris. The fluid drains back into the bloodstream through sieve-like channels called the trabecular meshwork. Normally, the amount of fluid produced is balanced by the amount draining away, so the pressure in the eye stays constant.
What causes nerve damage?
Glaucoma, it's the raised pressure inside the eye that causes optic nerve damage. Pressure increases usually happens because the aqueous humour in the anterior chamber doesn’t drain away properly.
The cause of glaucoma is still not completely clear or understood. Some people have high internal eye pressure but do not end up with optic nerve damage, while in others the nerve becomes damaged despite normal internal eye pressure.
Other factors, such as a weakness in the nerve or poor blood supply to the optic nerve, may also be add to the problems.
Types of glaucoma
The two main types of glaucoma are; open angle glaucoma and closed angle glaucoma.
Open angle glaucoma is the most common in people and results when the trabecular meshwork becomes blocked over a period of time usually several years, this leads to gradual increase in pressure and decrease of vision.
The build up of pressure inside the eye is painless as well as slow. If this isn’t treated, as the optic nerve will be slowly and gradually damaged, the field of vision will reduce, eventually only a small area of central vision remains this is called tunnel vision, then sight is lost completely. Many people do not even notice any symptoms at all until they have a loss of vision which is noticed, and by this time optical nerves may be damaged. This is why we recommend regular screening tests for people over the age of 40 .
Closed angle glaucoma (also called acute glaucoma) is a lot less common. It involves a quick and complete blockage of the trabecular meshwork, and can result in permanent blindness if not treated instantly. Usually it affects only one eye, which becomes red and extremely painful. This may be accompanied by blurred vision, a headache, and but physicaly sick. Closed angle glaucoma needs instant treatment in hospital. This involves taking medicine to reduce the pressure in the eye, followed by laser eye treatment or surgery. The second eye is would be treated at the same time, because there is a strong chance it will develop the same problem. If treated quickly there can be almost complete and long term recovery of your vision.
There are two other less common types of glaucoma: secondary glaucoma, in which the rise in internal eye pressure is the result of another eye condition, and congenital glaucoma due to a physical abnormality of the eye present at birth.
Risk involved with Glaucoma
Risk involved for primary open-angle glaucoma include increasing age and a family history of glaucoma. It is more common in Afro-Caribbean people. Studies have shown that diabetes is a risk factor for primary open-angle glaucoma though there is no clear evidence of this.
Screening for and detecting glaucoma in eyes
Screening is the way to detect glaucoma before there is increased loss of vision. An optician can do these during a normal sight test. We recommend everyone over 40 should have their eyes checked for glaucoma at least every two years.
There are three types of simple, painless tests that an optometrist can do:
- Look at the back of the eye using a special torch (ophthalmoscope). Damage to the optic nerve can be seen at the back of the eye.
- Measure the internal pressure of the eye (tonometry). This is done with a device that blows a small puff of air onto the eyeball.
- Measure the field of vision, by showing a sequence of spots of lights and asking which can be seen.
People who are found to have glaucoma can be referred to a specialist eye doctor abroad (an ophthalmologist) for assessment and eye treatment.
Glaucoma eye treatment
Treatments for glaucoma should lower the internal pressure of the eye and prevent any loss of vision, or any further reduction in vision. Options include medicine eye drops, laser treatment and surgery. Any eye treatment or surgery cannot reverse any optic nerve damage already been done, so it won’t improve loss of sight if that has already decreased.
Medicine for Glaucoma
Different types of medicine available for treating glaucoma help lower the internal pressure of the eye by increasing the flow of fluid out through the trabecular meshwork, or by reducing production of increase of fluid. A beta-blocker such as betaxolol is often tried first.
Many other types of drugs are available in tablet and drop form, as alternatives or in addition to beta-blockers.
Important any prescribed eye drops should be used every day as advised by your doctor, or the pressure in the eye will rise again. Combination eye drops that are available might be more convenient for those who need to use two different medicines.
Side-effects: all eye drops can cause some irritation to the eyes. Beta-blockers can cause dry eyes and itching. Other Side-effects from other types of medicine can include tblurred vision, darkening of the iris, thickening and lengthening of eye lashes, headaches and taste disturbance.
Laser eye treatment
A laser would be used to widen or open the holes in the trabecular meshwork. This treatment is quick and causes some but low discomfort. General anaesthetic isn't required and a overnight stay in hospitalisn't required. The success of this type of treatment varies from person to person, and it may be necessary to carry on using eye drops after laser treatment, though often at a much lower dose.
Eye Surgery (trabeculectomy)
Newer medications and an increase of effectiveness of them for glaucoma has recently reduced the amount of traditional surgery for glaucoma. However, surgery is an option when medicines and/or laser treatment have failed to adequately lower pressure in the eye.
The operation is straightforward and involves creating a tiny opening in the eye wall, which allows fluid to escape into the loose tissue under the conjunctiva (the clear membrane that covers the white of the eye). From there it is absorbed back into the bloodstream. The operation often makes further treatment with eye drops or tablets unnecessary, but about one in five people need to keep using them.
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