Glaucoma: what is it?
Glaucoma is the name given to a group of eye diseases in which the optic nerve at the back of the eye is slowly and permanently destroyed.
In the glaucomas, the optic nerve dies at a faster rate than the rest of the body. The single greatest risk factor for this is raised pressure inside the eye though many people may have normal pressure inside the eye and still have glaucoma. Vision loss from glaucoma tends to start from the outside of the visual field and so is not noticed until it is too late. The best way to treat glaucoma is to lower the pressure in the eye.
Approximately 300,000 Australians have glaucoma. Generally there are no warning signs associated with this eye condition. The loss of sight is usually gradual and a considerable amount of peripheral (side) vision may be lost before there is an awareness of any problem. Glaucoma can’t be self-detected.
What are the symptoms of glaucoma?
Chronic (primary open-angle) glaucoma is the most common type. It generally has no warning signs in the early stages of development.
Damage progresses slowly and destroys vision gradually, starting with the side vision. One eye covers for the other and damage can go undetected until a significant amount of nerve fibres have been destroyed. This damage is irreversible. It is progressive and usually relentless. Treatment cannot restore lost vision but it can arrest or, at least, slow down the damage process. Early detection means that treatment can commence before a significant loss of vision occurs.
Who is at risk
Although anyone can get glaucoma, some people have a higher risk. They are those with:
- High eye pressure
- A family history
- Aged over 50
- African or Asian descended ethnicity
- Short sightedness
- A previous history of eye injury
- Past or present prolonged use of cortisone drugs (steroids)
- High or low blood pressure
It is recommended that people have a regular optic nerve check from age 50 and from age 40 for those of African or Asian descent. Those with a positive family history are generally checked from age 35 as they have a significantly increased risk. Most people are recommended to have an eye check for glaucoma every 2-3 years or when advised by their eye care professional.
What are the different types of glaucoma?
Chronic open-angle glaucoma
Chronic open-angle glaucoma is the most common form of this disease in Australians. However, other forms occur:
Low-tension or normal tension glaucoma
Optic nerve damage can occur in people even though they have low or normal eye pressure. This form of glaucoma is treated in a similar manner to chronic open-angle glaucoma.
Chronic angle-closure glaucoma
Chronic angle-closure glaucoma is a common form of glaucoma particularly in Chinese and South East Asians and more often needs laser treatment as well as eyedrops.
Acute angle-closure glaucoma
Acute angle-closure is when the pressure inside the eye rapidly increases due to the iris blocking the drain through which fluid travels out from the eye. An attack of acute angle closure is often severe. Symptoms are pain, nausea, blurred vision and redness of the eye. Immediate medical help should be sought. If treatment is delayed there can be permanent visual damage in a short time. Usually, laser surgery performed promptly can clear the blockage and protect against visual impairment. The narrow angles that lead to angle-closure can be opened by laser surgery, allowing fluid to leave the eye without obstruction.
Congenital glaucoma is a rare form of glaucoma caused by an abnormal drainage system. It can exist at birth or develop later. Parents may note that the child is sensitive to light, has enlarged and cloudy eyes which water excessively. Surgery is usually needed.
Secondary glaucomas can develop as a result of other disorders of the eye such as injuries, previous eye operations and/or inflammation. The prolonged use of cortisone (steroid) medication has a tendency to raise eye pressure and therefore can lead to secondary glaucoma.
How is glaucoma detected?
Comprehensive eye examinations are the best way to detect glaucoma. A glaucoma assessment can include the following:
- A check of the optic nerve (the nerve of sight) with an ophthalmoscope;
- An eye pressure check (tonometry);
- Visual field assessment. This checks the sensitivity of the side vision, where glaucoma strikes first;
- An imaging analysis (GDx, HRT, OCT);
- A cornea thickness assessment (pachymetry).Regular eye examinations are the best way to detect glaucoma early.
Can glaucoma be treated?
Although there is no cure for glaucoma it can usually be controlled and further loss of sight either prevented or at least slowed down.
- Eyedrops – This is the most common form of treatment. They must be used as prescribed. Drops can be varied to best suit the patient and the type of glaucoma. In some cases oral medication may be prescribed.
- Laser (laser trabeculoplasty) – This is performed when the eye care practitioner deems necessary but particularly when eye drops do not stop deterioration in the field of vision. In some cases eye drops will need to be continued after laser. Laser does not require a hospital stay.
- Surgery (trabeculectomy) – In most cases this is performed after eye drops and laser have failed to control the eye pressure.A new channel for the fluid to leave the eye is created. It is most often performed in a day surgery.
Treatment can save remaining vision BUT it does not improve eye sight, nor repair vision loss due to nerve damage. Therefore early detection is paramount.
Last Reviewed: 31/12/2015
Reproduced with kind permission from Glaucoma Australia.
Glaucoma Australia. What is glaucoma? https://www.glaucoma.org.au/media/1245/english-info-brochure-2015.pdf (accessed 2015).
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