What is glaucoma?
Glaucoma is the leading cause of irreversible blindness both in New Zealand and Worldwide and refers to a group of diseases that cause damage to the nerve at the back of the eye leading to loss of vision (the optic nerve). It is called the ‘sneak thief of sight’ because the side vision is lost first without you realising it. If untreated and the glaucoma gets worse and the vision loss works it’s way inwards until you are left with only ‘tunnel vision’. This is when your central vision – that you use for activities like reading and driving becomes affected. If the glaucoma further progresses then total blindness will result.
Most types of glaucoma are due to the eye pressure (called intraocular pressure) being too high. The eye is filled up with a fluid called the aqueous humour. In the eye there is a ‘tap’ that is always making this fluid and a ‘drain’ where it leaves the eye (in an area called the drainage angle). In glaucoma, there is a problem with the drainage of fluid out of the eye that results in the eye pressure rising. It is this increase in eye pressure that damages the nerve of the eye.
Are there different kinds of glaucoma?
Another type of glaucoma is called Angle Closure Glaucoma (ACG). In this type of glaucoma the drainage angle closes up blocking the fluid from leaving the eye. The eye pressure can build up very rapidly leading to what is called ‘Acute Glaucoma’. This is the only type of glaucoma where patients can have symptoms – including a painful red eye, loss of vision, haloes around lights, and nausea and vomiting. This is an emergency that needs to be treated urgently to prevent permanent loss of vision.
Glaucoma can also be due to some other disease in the eye, previous trauma, or due to medications – these are called ‘Secondary’ glaucoma’s. Examples include pseudoexfoliative glaucoma, pigmentary glaucoma, uveitic glaucoma, neovascular glaucoma, and steroid-induced glaucoma.
What does high intraocular pressure mean?
The eye is filled with a fluid and the pressure inside the eye that this produces is called the intraocular pressure (IOP). Normal IOP is considered to be 10-21 mmHg with the average being 16 mmHg. Having an IOP above 21 mmHg is a risk factor for developing glaucoma.
What are the symptoms of glaucoma?
For most types of glaucoma including Primary Open Angle Glaucoma (POAG) there are no symptoms until the disease is very advanced. Patients do not often notice loss of side vision and it is only until the central vision is affected (that used for reading and driving) that they become aware that there is a problem. There is no redness, pain or other symptoms.
One type of glaucoma that does have symptoms is the acute (sudden onset) form of Angle Closure Glaucoma. These patients will experience severe symptoms including a painful red eye, loss of vision, haloes around lights, and nausea and vomiting.
How is glaucoma diagnosed?
Most patients with glaucoma are usually first identified by their optometrist. They are then referred to a specialist for further assessment. The diagnosis is made by measuring intraocular pressure, examining the patient’s optic nerve for signs of glaucoma and performing special tests. These tests include a visual field test – which maps out your entire vision and detects any loss of side vision. As well, patients may have a scan of the optic nerve called and OCT scan that also helps to diagnose glaucoma early.
Who is at risk of glaucoma?
Anyone can get glaucoma but there are some risk factors that do increase your chances. These include having a family history of glaucoma, being older than 50 years (although it can occur at any age), Caucasian or Asian ethnicity, high blood pressure, being short sighted (open angle glaucoma) or long sighted (angle closure glaucoma), and steroid medication like prednisone.
Does glaucoma cause blindness?
Glaucoma can cause blindness if diagnosed too late or not treated appropriately. These days, the treatment we have for glaucoma is very effective so as long as patients are diagnosed early and commenced on treatment the disease can be halted for almost all patients, although we still do not have a cure for the disease yet.
What is ocular hypertension?
This is a term that is used for patients with a high intraocular pressure (> 21 mmHg) but no other signs of glaucoma or vision loss. These patients are at risk for developing glaucoma and do need to be monitored. If the intraocular pressure is very high then they will need to be treated to reduce the eye pressure back to normal.
What is normal pressure glaucoma?
Some patients develop glaucoma even with a normal eye pressure. The exact cause for this type of glaucoma is not well established. It may be that they have a more fragile optic nerve that is susceptible to damage from even normal levels of eye pressure and/or there may a problem with blood flow to the optic nerve. Interesting, lowering the eye pressure does help to halt or at least slow the disease down.
What does being a ‘glaucoma suspect’ mean?
A glaucoma suspect is considered to be someone at risk of developing glaucoma and hence needs to be monitored on a regular basis. For example, patients who have a strong family history of glaucoma would be considered glaucoma suspects. In addition, patients with a borderline high intraocular pressure, or early optic nerve and visual field changes may be considered glaucoma suspects initially until the diagnosis is confirmed.
How is glaucoma treated?
The main aim of treatment in glaucoma is to lower the intraocular pressure (IOP). The more severe the glaucoma the lower the IOP needs to be.
For most patients, this can be achieved with medication in the form of eye drops. There are many different eye drops that can be used for glaucoma and sometimes more than one medication will be needed to control the IOP. Some patients do have problems with side effects from eye drops as well as remembering to use them on a regular basis.
Other options for treatment include laser or surgery. The laser treatment for Primary Open Angle Glaucoma is called Selective laser trabeculoplasty or SLT. This is very gentle, safe and effective treatment for this type of glaucoma and can be an alternative to eye drops for some patients. For Angle Closure Glaucoma a different laser procedure is performed called a Peripheral Iridotomy or PI. Surgery for glaucoma is generally considered a last resort when medication and laser treatment has been unsuccessful and there are several different surgical procedures available for glaucoma.
Are there any diet or lifestyle factors that affect glaucoma?
At present there is no clear evidence that diet has any influence on glaucoma however a healthy diet can help with other eye diseases like macula degeneration. There is also no evidence that vitamins or minerals help in glaucoma. Ginko biloba may help to improve blood flow to the optic nerves and may be recommended by your specialist if you have normal pressure glaucoma. There is no evidence to suggest that caffeine intake, alcohol or smoking is linked to glaucoma. Emotional stress is also not directly linked to glaucoma. However some studies suggest regular exercise can help to lower intraocular pressure.