Glaucoma is a group of eye diseases affecting the optic nerve. It is considered the second leading cause of blindness worldwide (after age-related macular degeneration). Glaucoma affects 1 in 50 Australian adults, yet concerningly, half of the people with glaucoma don’t actually realise they have it.
What is Glaucoma?
Glaucoma is an eye disease characterised by irreversible optic nerve damage. The optic nerve is responsible for carrying neural signals from the eye to the brain to enable vision.
In most cases, glaucoma is associated with high eye pressure, also known as intraocular pressure. Intraocular pressure is the pressure inside the eyeball, and like blood pressure throughout the body, we want it to be within a certain range to maintain the health of the eye.
Intraocular pressure is determined by how much fluid is inside the eye. This fluid, known as aqueous humour, is constantly being produced but must also be able to flow out via channels known as the drainage angle. This angle, also known as the anterior angle, is the channel created between the coloured iris and the transparent cornea at the front part of the eye. Too much fluid being produced in comparison to drainage results in an increase in eye pressure.
There are many different types of glaucoma, even congenital glaucoma (present at birth), but this eye disease can be broadly classified into three categories.
Primary Open Angle Glaucoma
Primary open-angle glaucoma occurs when the drainage angle is unobstructed, yet there is still a rise in intraocular pressure and subsequent damage to the optic nerve. Open-angle glaucoma accounts for about 90% of glaucoma patients in Australia.
While “primary” implies there is no identifiable cause, it is also possible to have secondary open-angle glaucoma. These are types of glaucoma involving an open angle, but there’s a known reason why the eye pressure is elevated. Examples include the drainage channel being blocked by pigment (pigmentary glaucoma) or damage to the drainage angle from eye injuries (traumatic glaucoma).
Acute Angle Closure Glaucoma
Conversely, acute angle closure glaucoma occurs when the iris sits too close to the cornea, narrowing the drainage channel and impeding the outflow of aqueous fluid. Compared to open-angle glaucoma, which typically involves a gradual increase in eye pressure, acute-angle closure glaucoma usually presents with a sudden, very high eye pressure spike. This makes it more likely to cause visual symptoms.
Normal tension glaucoma, or low tension glaucoma, occurs when the optic nerve experiences damage while eye pressures remain within normal range. The reasons for normal tension glaucoma are less well understood, but one theory is compromised blood flow to the optic nerve.
What Does Glaucoma Vision Look Like? The Most Frequent Visual Symptoms Reported by Patients With Glaucoma
As the majority of glaucoma cases involve open-angle glaucoma and a slow rise in eye pressure, for most people, the early stages of the disease tend to be asymptomatic with few visual symptoms, if any. This means that early detection with regular eye exams is your best chance of preventing vision loss.
Open-Angle Glaucoma Symptoms
This form of glaucoma presents with no early signs. There is no pain, redness, or noticeably blurred vision. Yet the damage to your optic nerve is slowly and subtly affecting your peripheral vision. Peripheral vision refers to the sight around the edges of your visual field.
Because we are much less attentive to the details in our peripheral vision compared to our central vision, vision loss of peripheral vision is harder to notice until in the more advanced stages. Although tunnel vision is often listed among the most common visual symptoms reported, one study found that patients were less likely to report tunnel vision. Instead, common symptoms included needing more light, blurry vision, feeling there was too much light, missing or darkened patches of vision, or feeling as if they were looking through dirty glasses.
Angle-Closure Glaucoma Symptoms
Angle-closure glaucoma is a medical emergency involving very high eye pressure that can cause significant optic nerve damage and vision loss in a short amount of time. Frequent visual symptoms mentioned include sudden blurred vision, watering eye, and seeing haloes around lights. Other symptoms include severe eye pain, redness, and even nausea and vomiting.
Because vision loss from glaucoma is permanent and there are often few symptoms in the early stages, regular eye exams are crucial to detect glaucoma early and preserve normal vision. There is currently no cure for glaucoma, but timely treatment can slow or prevent further vision loss.
If the angle is open, glaucoma is often treated with eye drops to lower the eye pressure. These eye drops may need to be used multiple times a day, and you may need more than one drop to manage the pressures. Some glaucoma patients benefit from a laser treatment called selective laser trabeculoplasty to improve the outflow of aqueous fluid.
Another option is eye surgery, including the insertion of microscopic stents or shunts as another outlet for fluid to drain out.
Closed-angle glaucoma is a medical emergency. First aid can involve administering oral medication to lower the pressure, followed by laser surgery.
Risk Factors for Glaucoma
Though it’s not possible to prevent glaucoma, you can remain vigilant to any increased risk by understanding your risk factors and attending your regular comprehensive eye exam with either an optometrist or eye doctor.
At your comprehensive eye exam, your eye doctor will routinely check your eye pressure and look at your optic nerve. You may also have a scan known as optical coherence tomography (OCT) to take more detailed measurements of the optic nerve, as well as a visual field test to map the sensitivity of your peripheral vision. Visual field testing and OCT scanning are useful for detecting and monitoring all types of glaucoma, from early or moderate glaucoma to advanced glaucoma.
Factors contributing to an increased risk of glaucoma include:
- Older age
- Family history of glaucoma
- A thin cornea
- History of eye injury
- Low or high blood pressure
- Having long- or short-sightedness
Remember that vision loss from glaucoma starts subtly but is irreversible. You can detect glaucoma early by having regular eye tests and being mindful of your risk factors.
Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.
Vision problems among older Australians.
What Do Patients with Glaucoma See? Visual Symptoms Reported by Patients with Glaucoma.