Glaucoma is a group of diseases that can damage your eye’s optic nerve and result in vision loss and blindness. It is one of the leading causes of blindness in Australia, affecting approximately 3% of the population.
Glaucoma is a complex disease associated with 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 fibers, transmits the message of sight from the eye to the brain. The nerve fibers 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
How fluid circulates in the eye
To understand what’s happening with glaucoma, imagine the eye as a bathtub with water. The clear fluid inside the eye, the aqueous humor, is always flowing through the eye, just like an open faucet. As long as the drain is open, the tub won’t overflow. But if anything happens to block the drain, the water level rises and spills over the edge.
Any blockage in the drainage system of the eye (trabecular meshwork) creates a similar problem, but the fluid has nowhere to overflow. Rather, the fluid pressure increases and 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
Open angle glaucoma
Although there are many different causes of glaucoma, there are two broad categories, open angle glaucoma and narrow 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 the pressure to gradually increase inside the eye, just as though you were standing in your shower and noticed the water rising. You look down at the drain and see nothing is blocking it. The clog is somewhere deep inside the drain. This form of glaucoma usually causes no pain or sensation. The vision is lost slowly, starting in the periphery so that it is generally not noticed until significant damage has occurred, unless it is detected earlier by your eye specialist.
Narrow Angle Glaucoma
The other major form of glaucoma is narrow angle glaucoma, also known as angle-closure glaucoma. This form of glaucoma can again be likened to your standing in the shower and noticing the water filling up in the tub. As you look down, you notice that your foot is covering the drain. The iris, the colored part of the eye, has moved forward, blocking the openings into the drainage system, causing a sudden rise in the pressure in the eye. This can result in halos around lights, severe pain and rapid loss of vision.
Glaucoma Risk Factors
It is estimated that there are 300,000 people in Australia with glaucoma with nearly 50% unaware they have the disease. Anyone can develop glaucoma however a person is at higher risk if any of the following are present:
- A family history of glaucoma
- Age – over 40 years
- Myopia (short sightedness)
- Eye injuries
- High blood pressure
- Past or present use of cortisone drugs (steroids)
- African ancestory
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 help minimize the 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, and can be discussed with your doctor.
- Eye drops are used to reduce fluid production in the front of the eye or to 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 minimize the 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.