What is glaucoma?
Glaucoma is not a single disease. It is a group of progressive eye conditions that damage the optic nerve, the critical cable that carries visual information from your eye to your brain. As that nerve deteriorates, your field of vision gradually narrows, often starting at the edges and working inward.
In most cases, the damage is linked to elevated pressure inside the eye, known as intraocular pressure (IOP). Fluid that normally circulates inside the eye fails to drain properly, pressure builds, and over time that pressure compresses and injures the optic nerve. Critically though, some people develop glaucoma even with normal eye pressure, and some people tolerate elevated pressure without damage. This is exactly why pressure measurement alone is not sufficient for diagnosis or detection.
The most common form of glaucoma has no pain, no redness, and no early visual symptoms. Peripheral vision is lost so gradually that most people don't notice until significant damage has occurred. By that point, vision cannot be restored.
Types of glaucoma
The two main categories behave very differently. One creeps up silently, the other can strike suddenly.
The most common type. Drainage channels become gradually less efficient over time. There are no warning symptoms. This is the type most people mean when they say "glaucoma."
The drainage angle between the iris and cornea is narrow or blocked. Can be chronic and silent, or can present as an acute attack with sudden eye pain, blurred vision and nausea, which is a medical emergency.
Optic nerve damage occurs even when IOP is within the normal range. More common in people of East Asian descent. Likely related to poor blood flow to the optic nerve.
Caused by another condition such as eye injury, inflammation, prolonged steroid use, or certain systemic diseases. Treatment addresses both the underlying cause and the elevated pressure.
How glaucoma takes your vision
Glaucoma progresses in predictable stages, but those stages are often invisible until it's too late to act.
Optic nerve fibres begin to die. Peripheral vision is subtly narrowing. No pain. Nothing you can feel or notice.
Side vision loss is measurable on testing. You may still not notice, as the brain compensates by filling in gaps. Daily activities feel normal.
Only a narrow central field of vision remains. Tasks like driving become dangerous or impossible. This is when most people are first diagnosed.
Without treatment, most remaining vision is lost. This is irreversible. There is currently no way to restore sight lost to glaucoma.
When caught early, glaucoma can almost always be managed. Eye drops, laser procedures, or surgery can reduce intraocular pressure and halt or significantly slow progression, protecting the vision you have left. Early detection is everything.
What glaucoma does to your vision
Symptoms
One of the most dangerous things about glaucoma is that, in its most common form, it produces no noticeable symptoms until a significant amount of vision has already been permanently lost.
The most common type of glaucoma, primary open-angle glaucoma, develops slowly over months or years without pain, redness, or noticeable vision changes. Because it typically affects peripheral (side) vision first, your brain compensates by filling in the gaps. Most people are completely unaware anything is wrong until the disease has progressed to a moderate or advanced stage.
Glaucoma usually begins by eroding your peripheral vision, the outer edges of what you can see. This creates blind spots that expand gradually. Because we rarely notice our peripheral vision consciously, these losses typically go undetected in everyday life. You may bump into things more often or miss objects to the side, but these changes happen so slowly that most people attribute them to other causes.
The sharp, detailed central vision you use for reading, driving, and recognising faces is usually preserved until late in the disease. This is why many people with glaucoma still feel their vision is "fine" even when significant peripheral damage has occurred. By the time central vision is noticeably affected, the disease is typically advanced.
Unlike the gradual, silent progression of open-angle glaucoma, acute angle-closure glaucoma can strike suddenly and is a medical emergency. Symptoms include severe eye pain, sudden blurred vision, halos around lights, nausea and vomiting, headache, and a red eye. If you experience these symptoms, seek immediate emergency medical attention. Acute angle-closure glaucoma can cause permanent vision loss within hours if untreated.
Because glaucoma is usually symptom-free until late stages, routine screening and awareness are the only reliable ways to catch it early. G-Screen's educational risk check includes a peripheral vision test that can help highlight potential areas of concern worth discussing with your optometrist. It is not a substitute for a comprehensive eye examination.
Who is at risk?
Glaucoma can affect anyone, but certain factors significantly increase your likelihood of developing it. If any of these apply to you, regular eye checks are especially important.
- Family history of glaucoma You are 10 times more likely to develop glaucoma if a direct family member has it. First degree relatives have almost a 1 in 4 chance in their lifetime.
- Age over 50 Risk increases significantly with age. By age 80, around 1 in 8 people have glaucoma.
- High eye pressure Elevated intraocular pressure is the most significant modifiable risk factor, though not present in every case of glaucoma.
- African or Asian descent Primary open-angle glaucoma is more prevalent in people of African descent, while normal tension and angle closure glaucoma are more common in those of Asian descent.
- Diabetes People with diabetes are approximately twice as likely to develop glaucoma compared to those without.
- Short or long sightedness Both myopia and hyperopia are associated with increased glaucoma risk.
- Prolonged steroid medication use Long term use of corticosteroid eye drops, tablets, or skin creams applied near the eyes can elevate eye pressure over time.
- Previous eye injury or surgery Trauma to the eye can disrupt normal drainage and lead to secondary glaucoma, sometimes years after the original injury.
- Migraines There is an established association between migraines and glaucoma risk, likely related to vascular factors affecting the optic nerve.
- Obstructive sleep apnoea People with sleep apnoea have a higher prevalence of glaucoma, with intermittent low oxygen levels thought to play a role.
Other known risk factors include high or low blood pressure, thin corneas, and certain systemic conditions. Talk to your optometrist if you have any concerns.
How is glaucoma detected?
Because glaucoma has no early symptoms, detection requires testing and it cannot be self-diagnosed. An optometrist is usually the first point of contact for glaucoma detection in Australia. As part of a comprehensive eye exam, your optometrist will assess intraocular pressure, examine the optic nerve head, perform visual field testing, and in many cases use OCT imaging of the retinal nerve fibre layer.
If your optometrist identifies signs of glaucoma or suspects you may be at risk, they will refer you to an ophthalmologist. An ophthalmologist is a medical doctor specialising in eye disease who can confirm the diagnosis, determine the type and severity of glaucoma, and prescribe treatment.
Crucially, measuring eye pressure alone is not enough. Up to 40% of people with glaucoma have normal IOP readings, meaning a single pressure test gives a false sense of security. This is why a thorough, multi-component assessment is the gold standard.
Online tools like G-Screen use validated visual field testing to help identify people who warrant a full clinical assessment. They are not a diagnosis, but they are a meaningful first step, especially for people who have never had their eyes examined or who face barriers to accessing care.
Glaucoma Australia recommends all Australians aged 50 and over visit an optometrist every two years for a comprehensive eye exam. If you have a family history of glaucoma or are of Asian or African descent, that recommendation starts at age 40. If you have any other risk factors, speak to your optometrist now regardless of age.
How is glaucoma treated?
Glaucoma cannot be cured and vision already lost cannot be restored. However, when detected early, treatment can halt or significantly slow progression and protect the vision you have left. The goal of all treatment is to lower intraocular pressure to a level that reduces further optic nerve damage.
The most common first line of treatment. Medicated drops are used daily to either reduce the amount of fluid the eye produces or improve how well fluid drains. They are effective for most people and are usually the starting point before other interventions are considered.
Selective laser trabeculoplasty is a quick, painless procedure that improves fluid drainage from the eye. It is increasingly used as a first line treatment alongside or instead of drops. Effects can last several years and the procedure can be repeated if needed.
MIGS procedures use microscopic instruments to improve drainage with a much lower risk profile than conventional surgery. They are often performed at the same time as cataract surgery and are well suited to mild to moderate glaucoma.
Trabeculectomy and drainage device implants are used when other treatments have not adequately controlled eye pressure. These procedures create a new drainage pathway and are typically reserved for more advanced or difficult to control cases.
Glaucoma requires ongoing management. Eye drops must be used consistently every day and regular monitoring with an ophthalmologist is essential to ensure pressure remains controlled and progression is detected early.
Think you might be at risk?
G-Screen's free online check takes around 6 minutes and uses a validated visual field test to assess your risk.
No appointment. No cost.
Developed with leading glaucoma specialists.