What is Glaucoma?
Glaucoma is an eye condition resulting in irreversible optic nerve damage. The condition can affect your vision so gradually that you may not notice any loss of vision until the disease is at an advanced stage. Therefore, early diagnosis and treatment are key in minimising or preventing optic nerve damage and limiting related vision loss.
Glaucoma may be caused by raised eye pressure, a weakness in the optic nerve or a combination of both. Intraocular pressure (IOP) is the tissue pressure within the eye that allows the eyeball to maintain its shape. It is determined by the balance between the production and drainage of clear fluid inside the eye. Over-production or obstruction of the fluid can cause an increase in the IOP, which results in damage to the optic nerve. The optic nerve is the site where all the sensitive nerve fibres around the retina come together to send the visual signal to the brain. It is damage to this optic nerve that causes irreversible visual loss affecting the field of vision. However, high IOP does not always cause glaucoma, but if you do experience a higher than normal level of pressure in your eye, you should always consult with an ophthalmologist.
There are several types of glaucoma which can affect the eye, and these are typically classified as follows:
1 Open-angle Glaucoma
Open-angle glaucoma happens when the drainage canals become clogged over time or when the tissues around the canals harden. Poor fluid drainage out of the eye results in increased eye pressure. Most patients have no symptoms and no early warning signs.
Initially, open-angle glaucoma has no symptoms and causes no pain. It can develop in one or both eyes. Without treatment, individuals will slowly lose their peripheral (side) vision. As it remains untreated, people may miss objects to the side and out of the corner of their eye. They seem to be looking through a tunnel. Over time, straight-ahead (central) vision may decrease until no vision remains.
2 Angle-closure Glaucoma
Angle-closure glaucoma is caused by a shallow space between the iris and cornea. Fluid drainage is obstructed if the iris slips forward. This condition is triggered by medication that dilates the pupil or occurs naturally when the eye dilates in low lighting. Hyperopic (Long-sighted) patients are at a higher risk because their eyes have narrow drainage angles. Symptoms include severe eye pain, blurred vision, nausea and vomiting.
Those more at risk of developing angle-closure glaucoma include:
• Anyone with hyperopia (long-sightedness)
• Women (4 times more likely)
• Anyone over the age of 50
3 Low-tension Glaucoma
Low-tension glaucoma is a condition in which the optic nerve is damaged and vision loss has occurred despite normal pressure in the eye.
4 Congenital Glaucoma
Congenital glaucoma is present at the time of birth.
Who is affected?
Although anybody can get glaucoma, certain individuals carry a higher risk. These include people who:
- Are over the age of 40
- Have a family history of glaucoma (You’re 4 times more at risk of developing the condition if a close blood relative – parent or sibling – has the condition)
- Suffer from myopia (short-sightedness) or hyperopia (long-sightedness)
- Have blood pressure problems
- Have diabetes
- Are regular, long-term steroid/cortisone users