What is Glaucoma?
Glaucoma is a group of diseases that damage the eye’s optic nerve and can result in vision loss and blindness. Over 300,000 Australians are affected by glaucoma and 80 million worldwide. It is the second most common cause of blindness worldwide after cataracts. With early detection and treatment, patients with glaucoma can often protect your eyes against serious vision loss.
It is for this reason that everyone over the age of 45 should see their optometrist for eye check every 2 years and earlier if there is family history.
Glaucoma is usually associated with an intraocular pressure (IOP) above the normal range. However:
- 20-52% of patients with glaucoma have IOP within the normal range. Patients with normal IOP who develop the characteristic changes associated with open-angle glaucoma are said to have low tension or normal pressure glaucoma.
- Many patients have raised IOP for years without developing the changes of glaucoma. This condition is referred to as ocular hypertension.
Often glaucoma can develop without any symptoms. There is commonly no pain and central vision often stays normal until it is late stage of the disease. Therefore it is important for patients with glaucoma to have regular specialized visual field test to assess the amount of peripheral (side) vision being affected.
Without treatment, people with glaucoma will slowly lose their peripheral (side) vision. As glaucoma 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.
Glaucoma can develop in one or both eyes.
Glaucoma can be classified as open angle or close angle.
In angle-closure glaucoma, the fluid at the front of the eye cannot drain through the angle and leave the eye. The angle gets blocked by part of the iris. This type of glaucoma is more common in Asian patients. People with this type of glaucoma may have a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. If you have these symptoms, you need to seek treatment immediately. This is a medical emergency. Without treatment to restore the flow of fluid, the eye can become blind. Using laser to create a small channel on iris near the angle can prevent this emergency from occurring, this is called laser peripheral iridotomy. (More information on page on Peripheral Iridotomy)
In open-angle glaucoma, the drainage angle is not blocked by iris. Open-angle glaucoma forms the majority of glaucoma in Australia. In open-angle glaucoma, even though the drainage angle is “open”, the fluid passes too slowly through the meshwork drain. Since the fluid builds up, the pressure inside the eye rises to a level that may damage the optic nerve. When the optic nerve is damaged from increased pressure, open-angle glaucoma-and vision loss—may result. That’s why controlling pressure inside the eye is important.
There is no single value of eye pressure that will cause glaucoma. The damage to the optic nerve occurs when the balance between eye pressure and the optic nerve’s ability to handle pressure is lost.
Some people are at higher risk than others:
- People with a family history of glaucoma
- Older age
- Patient with migraines, Raynaud’s condition (a condition that causes very cold fingers and feet) or low blood pressure especially at night.
- Some patient with obstructive sleep apnoea
- Eye specialist will discuss with their glaucomations the safe eye pressure for their eyes (known as target pressure).
How is glaucoma diagnosed?
For detection of glaucoma your eye specialist will perform a comprehensive eye examination to examine the eye pressure, drainage channels of your eye and optic nerves.
Your eye specialist can measure your eye pressure with specialized machine called the tonometer. He or she will also use a special machine to measure the thickness of your cornea called pachymetry. This is important because a thin cornea can cause artificially low eye pressure, and a thicker cornea can cause artificially high eye pressure.
Additional tests you will have include:
- Visual field test. This test measures your peripheral (side vision). It helps your eye care professional tell if you have lost peripheral vision, a sign of glaucoma.
- OCT (optical coherence tomography) scan. This test uses non-invasive and safe laser to assess the amount of neural tissue present in your optic nerve and the population of neural cells (ganglion cells) in the retina. The OCT and visual field test forms an integral part of documenting the structure and functional changes caused by glaucoma. It is important for diagnosis of glaucoma as well as assessing whether there has been any progression.
- Optic nerve photography. This is a special photograph of the optic nerve to document its appearance for future reference.
In addition, Dr George Kong co-invented the worlds first home monitoring app on Apple iPad that allows patients to perform visual field test at home. If you use this software app it will allow your eye specialist to monitor your glaucoma more frequently, therefore able to detect any worsening of glaucoma early.
Can glaucoma be cured?
The peripheral vision lost from glaucoma cannot be restored. There is no cure for glaucoma, however there is ample evidence from multiple clinical trials to show that if the eye pressure (IOP) is lowered to a safe level then glaucoma will not get worse (will not progress).
Therefore the most important aspect of glaucoma management is EARLY DETECTION and PREVENT PROGRESSION.
What is the safe eye pressure for you may be different to other people. Many factors needs to take into consideration including your age, the degree of existing glaucoma damage and cornea thickness etc. Your eye specialist will talk to you to work out the eye pressure that will be safe for the eye (Known as the Target eye pressure).
Treatment for glaucoma
Treatment for glaucoma – stage glaucoma can delay progression of the disease. That’s why early diagnosis is very important.
Glaucoma treatments include:
- Eye drops – These are the most common form of treatment for glaucoma. Patients will need to use these on a daily basis and therefore compliance is important. Less commonly commonly tablets called Diamox may be used, however with much more side effects.
- Selective Laser Trabeculoplasty (SLT) – SLT is a non-invasive laser procedure that treats the drainage channels in the eye to encourage greater fluid flow. It can be in addition to eye drop treatment or can be used instead of eye drop treatment.
- Minimally invasive glaucoma surgery (MIGS) – MIGS involves various micro devices to allow aqeous drainage out of the eye with less trauma and post-operative complications than conventional surgery. The long term effectiveness of these procedures are not clear.
- Conventional surgery (Trabeculectomy or Tube shunt operation) – These are drainage procedures performed when medical, laser therapy or MIGS have failed. The long term effectiveness of these procedures are well established however post-operative complications are significant.
- Cyclodiode laser – Cyclodiode laser treatment is commonly used in intractable glaucoma or eyes with poor vision or a combination of any of these.
The aim of these treatments is to prevent any progression of your glaucoma by achieving a pressure that is safe for the eye.