What is Glaucoma?
Glaucoma is a family of eye conditions with a typical optic neuropathy (loss of nerve cells in the back of the eye) which can lead to a progressive loss of peripheral vision and can result in blindness. For most of these conditions raised Intra Ocular Pressure (IOP) is considered to be the key driver of the disease. For practical purposes pressures above 21 mmHg (millimeters of mercury) are considered abnormal - though as is common in medicine there are exceptions. In most cases lowering the IOP greatly slows the progression of the disease and if the pressure in the eye is kept low most patients preserve their sight.
How do I know if I have Glaucoma?
There are 2 more common types of Glaucoma and a range of other less common forms: Primary Open Angle Glaucoma (POAG) and Angle Closure Glaucoma (ACG). POAG normally creeps up on people slowly. Angle Closure Glaucoma can also creep up slowly but can also present with a sudden very painful eye and cloudy vision.
￼ Glaucoma is a disease where a “stitch in time saves nine”. It needs to be detected early and managed if sight loss is to be prevented. The most common early sign of glaucoma is the loss of the very edge of the visual field (your peripheral vision). As we do not use this part of vision, much this can go un-noticed by the patient. By the time patients are aware of visual field loss the condition is normally advanced and difficult to manage.
Unfortunately the early signs of glaucoma can only be detected by an ophthalmologist (eye doctor) or a skilled optometrist. There are 3 principle abnormalities that help make the diagnosis. The Intra-ocular pressure, the visual field and the physical appearance of the optic nerve head (the back of the eye where the nerves carrying the visual information for the brain exit the eye). Any of these measurements alone can not be used to make a diagnosis of Glaucoma, but need to be used together - often with further measurements and observations such as corneal thickness and an examination of the drainage angle of the eye (gonioscopy).
Eye pressure measurements are frequently done by optometrists and abnormal measurements should generate a referral to an ophthalmologist (eye doctor). However, as is often the case in medicine, even a “normal” measurement does not always mean all is well.
Visual fields are also frequently measured by thorough optometrists and these can demonstrate field loss. ￼ Field loss is not only caused by glaucoma and the list includes some very serious diseases - so it is best to have visual fields interpreted by an appropriately trained doctor with detailed knowledge not only of the eye but also the whole visual pathway. This stretches from the eye right through the brain to the occipital lobe at the back of the skull where visual data is processed into vision, passing a number of important structures on the way.
The optic nerve head, also known as the optic disc, (the back of the eye where the nerves carrying the visual information for the brain exit the eye) shows characteristic changes in glaucoma: in particular the number of nerves exiting the eye carrying visual information is reduced. The result is a change in what is called the “cup to disc ratio". This sign can be seen by an ophthalmologist or experienced optometrist using special lenses at a slit lamp. The optic nerve head can also be imaged with sophisticated machines - but no matter how it is examined the information still needs to be interpreted carefully before the correct diagnosis can be made.
In summary, despite sophisticated testing and imaging it is still important to see an experienced glaucoma practitioner. This is important to avoid the twin problems of unnecessary over treatment or sight threatening under treatment of aggressive disease. If a full and careful exam is not conducted, including a formal assessment of the trabecular meshwork (the drainage area where fluid leaves the eye), normally with another special lens called a gonioscopy lens, it has been shown that both over diagnosis and under diagnosis occurs1.
Who Gets Glaucoma?
Any one can get glaucoma. It is thought to affect around 3% of the general Australian population over 49 years of age and over 4% of the general Australian population over 70 years of age. ￼There are clear racial differences. Angle Closure Glaucoma (ACG) is rare in Africans and Europeans. ACG is thought to affect only around 0.4% of people of European decent, but is the most common form of Glaucoma in South East Asians, affecting 3% of the population in East Asians. The most common form of Glaucoma in Australia generally, Primary Open Angle Glaucoma (POAG), occurs in 3% of Australians over 492 (of generally european descent), but affects 6.8% of West Africans over the age of 40, and can be more aggressive.
A close relative with Glaucoma will increase your risk of developing the disease. If you know someone in your immediate family with Glaucoma you should ensure that your eyes are checked periodically.
Are there different types of Glaucoma?
Though Primary Open Angle Glaucoma (POAG) and Angle Closure Glaucoma (ACG) are the most common types of Glaucoma in Australia, there are a range of other types. These include Pigment Dispersion Glaucoma, Pseudoexfoliation Glaucoma, Inflammatory and Uveitic Glaucoma (including Posner-Schlossman and Fuchs Heterochromatic Uveitis), steroid induced Glaucoma, trauma and other even rarer causes.
Is it important to get my eyes checked?
It is vital to get your eyes checked regularly - either by an expert ophthalmologst (eye doctor) at the Moreton Eye Group or by a local eye doctor or expert optometrist. Only an eye exam can detect the early signs of Glaucoma and early treatment, where needed, is vital to preserve sight. Remember there is no “cure” for Glaucoma, only treatments that can slow its progression.
How is Primary Open Angle Glaucoma (POAG) treated?
POAG is normally treated with eye drops that lower the pressure in the eye. For the majority of patients a single drop to the eye each evening is all that is required to prevent the progress of the disease and to preserve sight. ￼For some however more than one drop may be required and if this fails, laser treatment or surgery is normally required. Selective Laser Trabeculoplasty (SLT) is non-invasive (does not involve cutting into the eye) and can delay surgery in many. Other minimally invasive methods, or opening up the drainage system of the eye, such as stents, are starting to be used. The principle operation for glaucoma control is called a trabeculectomy. It can be associated with side effects - even many years after otherwise highly successful surgery. Because of this complication rate other less invasive procedures are actively being developed.
In patients with POAG and cataract sometimes the removal of the cataract can in itself lower the pressure back to acceptable levels.
How is Angle Closure Glaucoma treated?
Angle Closure Glaucoma (ACG) can be chronic or acute. If you have chronic ACG you will probably be offered a small laser treatment called a peripheral iridotomy, or if you also have cataract, cataract extraction can also help. ￼Acute angle closure glaucoma can suddenly cause a blinding pressure rise in the eye which is painful and often (but not always) accompanied by a drop in vision. This is an emergency and requires immediate treatment by an ophthalmologist. If it happens out of normal office hours patients should go to an Emergency Department at a major hospital.
Are there risks with treatment?
The risks associated with the most common form of treatment, prostaglandin analogue eye drops, are small. Other drops can in rare cases cause side effects such as making the surface of the eye painful or asthma worse. Laser treatments are relatively low risk with an attractive side effect profile - but do not lower the pressure enough in all cases and the effect can reduce over time. If these non invasive treatments are not enough - or the condition is advanced - then surgery will be necessary. The main surgical operations, even in expert hands, can and do have a series of side effects. At the Moreton Eye Group we will discuss all of your eye concerns with you.
Is there anything I can do to prevent me getting Glaucoma?
Unfortunately there is no proven prevention for glaucoma. If caught early and progression is prevented by you working with your ophthalmologist then most patients can expect to have good sight for their whole lives. The key is to have an annual eye check and keep follow up appointments.