October 2020 - Armadale Eye Clinic

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.

Glaucoma Treatment

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.

Age-related macular degeneration is considered to be the leading cause of legal blindness in Australia, accounting for half of all cases of blindness. Unfortunately, the vision loss caused by macular degeneration is irreversible and there is currently no cure that can guarantee to halt the progression of any vision damage.

However, there are some steps that can be taken to reduce your risk of developing the disease or suffering further vision loss in the presence of existing macular degeneration.

What is Macular Degeneration?

The macula is the anatomical part of the eye responsible for your central vision. The retina is the sensory layer of tissue lining the inside of the eyeball; the macula is a part of this that contains the highest density of photoreceptors, the sensory cells that detect and respond to light before the signals are converted to neural impulses that are then sent onward to the brain for visual processing.

Macular degeneration is a disease that results in damage to the retinal tissues that support the high-energy function of these photoreceptor cells, known as the retinal pigment epithelium. Although there is still much more to understand about exactly why and how the damage occurs, we know that during age-related macular degeneration, metabolic waste material known as drusen begins to accumulate beneath the retinal pigment epithelium, interfering with the health and function of these tissues.

The resultant effect is that the photoreceptor layer, dependent on a healthy retinal pigment epithelium, also becomes damaged, leading to the characteristic macular degeneration symptoms of central vision deterioration. In more advanced stages of macular degeneration, known as the neovascular form, new blood vessels form under the retina, which is fragile and can leak blood and fluid, causing severe retinal damage and vision loss.

There are several risk factors associated with the development of age-related macular degeneration. Some of these are modifiable lifestyle choices while others are simply the luck of the draw.

Age – the risk of macular degeneration increases with increasing age
Family history of the disease – those with an immediate family member with macular degeneration are 50% more likely to develop the condition themselves
Smoking – cigarette smoking has been linked with a 3 to 4 times increased risk of developing macular degeneration compared to a non-smoker, and smokers are also at risk of encountering the disease 5 to 10 years earlier than a non-smoker with all other things being equal
Systemic conditions – certain diseases, such as obesity and hypertension, have been linked to an increased risk of macular degeneration

Macular Degeneration Symptoms

In most cases, macular degeneration symptoms occur gradually, and an individual with the disease may not even be aware of any changes to their vision for years. Macular degeneration symptoms can also be non-specific, meaning that they are not unique to macular degeneration and may be dismissed by a patient thinking they simply need an updated spectacle prescription.

Typically, macular degeneration symptoms can include:

Blurring of your central vision – this may not be immediately identifiable, but instead you may first begin to become aware of increasing difficulty with specific tasks that require detailed vision, such as reading text or recognising faces from a distance
Distortion in your vision – because of the formation of drusen disrupts the uniform, smooth layers of retinal tissues, you may see straight lines as wavy or curved
Dark patches in your vision – significant areas of photoreceptor damage and death will result in complete loss of vision in that particular area of your retina, which you may perceive as a black hole in your field of view
Sudden loss of central vision – in the case of wet macular degeneration, the loss of sight can be quite dramatic if a large retinal bleed were to occur

Your peripheral vision is likely to remain unaffected. Macular degeneration symptoms can differ in severity between the eyes, and in some cases may only present in one eye while the other eye experiences no issues at all.

Treatment

Currently, there is no treatment for dry macular degeneration. Management is aimed at addressing modifiable factors such as cigarette smoking and cardiovascular disease in an effort to slow the rate of vision deterioration. There are also nutritional factors that have been shown to be beneficial for the health of the macula, such as increasing your dietary intake of the antioxidants zeaxanthin and lutein.

For the wet form of macular degeneration, modern therapies are most commonly in the form of an injection of medication into the eye rather than retinal surgery. These medications are known as anti-vascular endothelial growth factor (anti-VEGF) drugs and are designed to block the proteins produced by the retina in wet macular degeneration that trigger the formation of new blood vessels.

Laser retinal surgery procedures such as photodynamic therapy are very rarely used in the modern management of macular degeneration nowadays; in specific cases it may be used as an adjunct treatment if the condition cannot be controlled entirely with anti-VEGF injections.

Another type of laser retinal surgery known as laser photocoagulation employs the use of a high-energy thermal laser that aims to destroy and seal leaking blood vessels. However, this treatment also results in damage to the surrounding retina and so is only used in the minority of cases where the formation of new blood vessels occurs in the retina some distance away from the crucial central vision.

As early intervention can help to identify what steps can be taken to reduce your risk of progressive vision loss from macular degeneration, it’s important to maintain regular eye examinations with your eyecare provider.