Glaucoma is a category of eye disease known as optic neuropathies. The optic nerve of the eye is responsible for carrying signals received by the sensory retina at the back of the eyeball all the way to the visual processing centres of the brain for what we call sight.
Considering that 2 out of every 100 of Australians will develop glaucoma in their lifetime, it’s not unlikely that you perhaps already know someone who has been diagnosed with the disease, or at least you’ve heard of the term. But what is glaucoma and how is treated, and more importantly, are there any early signs of glaucoma that you could look out for?
What Causes Glaucoma?
Glaucoma is diagnosed when the optic nerve suffers progressive damage due to an increase in the pressure of the eye, known as the intraocular pressure. In order to keep a healthy optic nerve, the normal intraocular pressure range is typically quoted as between 10-21mmHg (millimetres of mercury), however, it’s important to note that this does not mean that someone with intraocular pressures within this range will never develop glaucoma or someone with pressures slightly higher than this will definitely have glaucoma.
At a basic level, the intraocular pressure is determined by the balance of fluid production and drainage within the eye; this fluid is known as aqueous humour, and is different from the tears you secrete on the surface of the eye. If aqueous drainage is hindered for some reason, or if production is excessive, this will cause the intraocular pressures to rise.
Glaucoma is an extremely complex disease and doctors do not fully understand all the factors that interact and contribute to its development. We know that age plays a big role, particularly past the age of 50. People who have a direct family member with glaucoma are ten times more likely to develop it themselves, suggesting a genetic factor. Through research we have also noted various other associations with the risk of glaucoma, including the presence of sleep apnoea, diabetes, and myopia (short-sightedness).
The Signs of Glaucoma
Unfortunately, glaucoma has a nickname – the sneak thief of sight. This is because in the vast majority of cases, glaucoma, at least in the early to moderate stages, is actually asymptomatic.
In fact, half of people who have glaucoma are unaware they have the disease. There is a specific type of glaucoma called acute angle-closure glaucoma that can present with noticeable symptoms, such as severe pain, a red eye, and hazy vision, however, most people with glaucoma will have no warning until the more advanced stages of the disease when there is already marked vision loss.
The reason for this is because the optic nerve itself feels no pain from any damage, and the loss of vision from glaucoma typically begins in the periphery. If you think about which areas of your vision you’re most aware of, it’s your central vision – when you want to pay attention to something or someone, you will tend to look directly at it.
Peripheral vision is still important, such as noticing the movement of something coming towards you out of the corner of your eye, but we are less likely to be aware of changes and deterioration to the extremities of our visual field, particularly if they occur as slowly over time as happens during glaucoma. By the time a person with glaucoma does become aware that their peripheral vision has deteriorated, the disease is already likely in its advanced stages.
Because of this, regular eye exams with an eyecare practitioner, whether your local optometrist or, if you have strong risk factors for glaucoma, an ophthalmologist, is your best chance of diagnosing any glaucoma while the disease is still in its asymptomatic early stages. A thorough eye exam is able to detect the signs of glaucoma before you become aware of any issues and will involve tests such as:
- Measuring your intraocular pressure
- Examining the features of your optic nerves including its size and colour
- Taking scans of your retinal nerve fibre layer to detect any areas of thinning and damage
- Performing a visual field test to map the sensitivity of your peripheral vision
If glaucoma is detected, your eyecare clinician can commence appropriate glaucoma treatment immediately.
Luckily, the treatment of glaucoma is often quite effective. Although there is no currently existing cure that can reverse any vision loss that has already occurred or get rid of glaucoma altogether, timely glaucoma treatment aims to prevent or at least slow further vision loss.
A great deal of research is going into treatment for glaucoma as we understand more about the disease. All therapies aim to improve the balance between aqueous outflow and production, thereby reducing the intraocular pressure. Currently, available treatment options include:
- Eye drop medications – these are instilled at least once a day and will need to be taken long-term to keep the eye pressures under control
- Laser treatment – known as laser trabeculoplasty, some patients only require this once-off while others may need a repeat application a few years later
- Surgery – there are various effective surgical techniques to improve the drainage of aqueous humour from the eye, such as the insertion of a stent or shunt
Each treatment has pros and cons and one may be more suitable for an individual compared to another. The most important thing to remember is undiagnosed glaucoma cannot be treated – regular eye tests are your best bet at catching it early.
Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.