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.

Eye test 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.

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.

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.

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.  In North Brisbane this is the RBH.