Glaucoma is a group of diseases that can damage your eye’s optic nerve, resulting in vision loss and blindness.
Glaucoma is one of the leading causes of blindness in Australia, affecting approximately three per cent of the population.
It follows the build-up of fluid pressure inside the eye which, left untreated, can damage the optic nerve. The optic nerve, a bundle of more than a million nerve fibres, transmits the sight from the eye to the brain. Nerve fibres carrying peripheral vision are normally lost first. This reduction in side vision can be gradual and is not usually noticed. By the time it affects central or reading vision, tremendous damage to the nerve has occurred.
Causes and symptoms of glaucoma
Imagine the eye as a bathtub with water. The clear fluid inside the eye, the aqueous humor, is always flowing through the eye. As long as the drain is open, the tub won’t overflow. But if anything happens to block the drain, the fluid level rises and spills over the edge.
Any blockage in the drainage system of the eye (trabecular meshwork) creates a problem as the fluid pressure increases because the fluid has nowhere to go. This pressure damages one of the most sensitive and important parts of the eye – the optic nerve. Treatment, usually with simple eye drops, can prevent further loss of vision but cannot restore what has already been lost, therefore early detection is essential.
Types of glaucoma
The two broad categories of glaucoma are open angle glaucoma and narrow angle glaucoma.
Open angle glaucoma
The most common form is chronic open angle glaucoma. In this condition, a partial blockage in the drainage system of the eye causes a gradual increase in pressure. This form of glaucoma usually causes no pain or sensation. Vision loss is slow, starting in the periphery, so isn’t generally noticed until significant damage has occurred.
Narrow angle glaucoma
Narrow angle glaucoma, also known as angle-closure glaucoma, is where the iris, the coloured part of the eye, moves forward to block the openings into the eye’s drainage system, causing a sudden increase in pressure in the eye. This can result in halos around lights, severe pain and rapid loss of vision.
Glaucoma risk factors
An estimated 300,000 people in Australia have glaucoma, half of whom are unaware. Anyone can develop glaucoma, but you’re at higher risk with:
- A family history of glaucoma
- Aged over 40 years
- Myopia (short sightedness)
- Eye injuries
- High blood pressure
- Past or present use of cortisone drugs (steroids)
- African ancestry.
If you are in this risk group you should have your eyes checked for glaucoma no later than the age of 35. For everyone else it is recommended to have your eyes checked by age of 40 and every two years thereafter.
Once glaucoma has been diagnosed, treatment should begin as soon as possible to minimise risk of permanent vision loss. There is no cure for glaucoma, so treatment focuses on relieving symptoms and preventing further damage from occurring. Most cases of glaucoma can be treated with eye drops, laser or microsurgery. The best treatment for your individual case depends on the type and severity of the disease as well as your lifestyle.
Eye drops reduce fluid production in the front of the eye or help drain excess fluid, but can lead to redness, stinging, irritation or blurry vision. Patients should tell their doctor about any allergies they have to minimise risk of side effects.
Laser surgery for glaucoma aims to increase the outflow of fluid from the eye or eliminate fluid blockages through laser trabeculoplasty, iridotomy or cyclophotocoagulation.
Microsurgery involves a surgical procedure called a trabeculectomy, which creates a new channel to drain fluid from the eye and reduce the pressure that causes glaucoma. Surgery is often performed after medication and laser procedures have failed.