What is Glaucoma? Symptoms, Causes and Treatment

Glaucoma is not an uncommon disease. In fact, it is probably a lot more common than we realise. Glaucoma affects around one in every 50 Australians, and statistics tell us that about 50% of people do not even know they have it. Keep reading to find out more about what glaucoma is, what causes it, how it is diagnosed and the options for glaucoma treatment.

What is Glaucoma?

Glaucoma is a disease of the optic nerve. Because the optic nerve is crucial for carrying neural signals from the eyeball to the visual areas of the brain, if enough of these nerve fibres become damaged, it will result in slow and progressive vision loss. This vision loss typically starts in the periphery of your sight. This damage is irreversible. If glaucoma is left untreated, the loss can progress from the mid periphery of your field of view into tunnel vision, and eventually into complete blindness.

In many cases, glaucoma is associated with high eye pressure, commonly called intraocular pressure. However, the association between developing glaucoma and elevated intraocular pressures is not always straightforward. You may have intraocular pressures outside of the normal range but still have no evidence of glaucoma or optic nerve damage. Such cases may be termed ocular hypertension. Conversely, someone with intraocular pressures that are considered to be within normal may still show signs of vision loss from optic nerve disease. This is a type of glaucoma known as normotension or low tension glaucoma.

Glaucoma is also classified by the state of the drainage angle, the space between the iris and the cornea where fluid leaves the eye. It is described as open angle when that space is sufficient, and closed angle when it is compromised. Each form behaves differently, and our guide to the types of glaucoma covers them in detail.

What Causes Glaucoma?

At the moment, experts do not fully understand what causes glaucoma or why someone’s intraocular pressure might start increasing. We know that intraocular pressure is influenced by the balance of aqueous fluid production and drainage. If aqueous is unable to drain from the eye at the same rate as it is produced, the pressure inside the fixed volume of the eyeball will increase. If this high intraocular pressure persists, it can end up damaging the optic nerve and causing glaucoma.

While we do not always have an explanation as to why there may be an imbalance between aqueous production and drainage, some situations have a more obvious cause.

• Trauma to the eye can damage the fluid drainage structures
• Inflammation inside the eye can damage the drainage angle and reduce the outflow of fluid
• Narrowed drainage angles can physically restrict the outflow of aqueous fluid
• Anatomical anomalies to the eyeball may result in a poorly formed drainage structure, such as congenital malformations
• Changes to the relationship of anatomical structures inside the eye over time. For example, if a cataract develops, it can cause the lens to push the iris toward the cornea, which subsequently narrows the space around the drainage channels
• Free floating debris or pigment cells in the eye clog up the drainage channels
• Reduced blood circulation and oxygen supply to the optic nerve
• Underlying immune factors

There are also a number of factors associated with a higher risk of developing glaucoma. You may have none of these risk factors but still end up developing glaucoma. Conversely, you may have all these factors and never show evidence of glaucoma.

• Elevated intraocular pressures
• Older age, with risk rising steadily after 50
• Ethnic background, with African, Asian and Hispanic ancestry associated with higher risk
• Family history of glaucoma
• Corneas that are thinner than average
• High degrees of short or far sightedness
• The use of corticosteroid medications
• Diabetes
• Migraines or obstructive sleep apnoea

How is Glaucoma Diagnosed?

Glaucoma is almost always diagnosed during a routine eye test. In the vast majority of cases, the disease demonstrates no symptoms, leading doctors to nickname it the sneak thief of sight. If you are wondering what the early changes to your sight can actually look like, our guide on what glaucoma vision looks like covers this in detail.

Your optometrist or ophthalmologist may suspect you have glaucoma during a regular eye exam due to high intraocular pressures or an unusual appearance of your optic nerve. Glaucoma is often slowly progressive, so your eyecare practitioner may need more than one test result over time in order to have a clear diagnosis.

Common tests used to diagnose and monitor glaucoma include:

•   Tonometry to measure the intraocular pressure
•   Fundoscopy to view the optic nerve and assess its features
•   Gonioscopy to assess the drainage angles
•   Optical coherence tomography (OCT) to measure the thickness of the retinal nerve fibre layer and track the progression of nerve thinning
•   Visual field testing to map out any areas of sight loss in your peripheral vision

One type of glaucoma is different. Acute angle-closure glaucoma can present suddenly with a painful, red eye, vomiting and visual disturbances, and it is not unknown for people to mistake it for a stomach bug. These symptoms are a medical emergency. If you experience them, go to hospital immediately.

How is Glaucoma Treated?

If you are found to have glaucoma, your eyecare practitioner will discuss glaucoma treatment options with you. Glaucoma treatment is always aimed at lowering the intraocular pressure in order to protect the optic nerve.

Which option suits you is decided together with your ophthalmologist. It is worth discussing the side effects of each treatment, the potential complications, how much of a burden the routine will be day to day, and how effective it is likely to be at slowing the progression of your glaucoma.

Traditionally, first line treatment has been in the form of prescription eye drops, known as ocular antihypertensives. There are a number of different medications, and some need to be used up to three times a day. You may also need multiple types of drops to control the intraocular pressure.

If medications are found to be ineffective, or if you find it difficult to follow the dosing regime, your ophthalmologist may escalate your glaucoma treatment and recommend a laser procedure or surgery. One of the most commonly used laser procedures is known as selective laser trabeculoplasty. This involves using a laser to stimulate the removal of any debris blocking the drainage channels.

For closed angle glaucoma, a laser procedure called a peripheral iridotomy is used to create a small opening in the iris, which aids the drainage of aqueous fluid. Surgery is usually considered when intraocular pressure cannot be sufficiently controlled with other methods. Our guide to glaucoma treatment in Australia covers the full range of drops, laser and surgical options in more detail.

Since glaucoma typically does not present with any obvious symptoms, it is important to maintain regular eye tests with your eyecare professionals. This is especially true if you have any risk factors for glaucoma, including being aged over 50. There are also steps you can take to lower your risk, which we cover in our guide on how to prevent glaucoma.

Frequently Asked Questions

What are the early signs of glaucoma?

Glaucoma often develops without noticeable symptoms in its early stages. As the condition progresses, people may begin to lose peripheral (side) vision. Because early glaucoma symptoms can be difficult to detect, regular eye examinations are important for early diagnosis. You can see what glaucoma vision looks like in our dedicated guide.

Can glaucoma cause blindness?

Yes, glaucoma can cause permanent vision loss and blindness if left untreated. Damage to the optic nerve cannot usually be reversed, which is why early detection and treatment are essential for preserving vision.

Can glaucoma be cured?

There is currently no cure for glaucoma, and vision already lost cannot usually be restored. However, glaucoma treatment can often slow or stop further damage to the optic nerve and help preserve remaining vision.

What is the most common type of glaucoma?

Primary open angle glaucoma is the most common form of glaucoma. It develops gradually over time and often causes no symptoms until significant vision loss has occurred. Our guide to the types of glaucoma explains how each form differs.

Is glaucoma hereditary?

Yes, glaucoma can run in families. Having a parent or sibling with glaucoma significantly increases your risk of developing the condition. People with a family history of glaucoma should have regular eye examinations.

Can glaucoma be prevented?

Glaucoma cannot always be prevented, but the risk of significant vision loss can be reduced. Regular eye examinations, managing conditions such as diabetes and following your ophthalmologist’s advice all help. Our guide on how to prevent glaucoma goes into more detail.

Speak with our ophthalmologists

If you have questions about your eye health or would like a comprehensive eye assessment, contact the ophthalmologists at Mornington Peninsula Eye Clinic on (03) 9070 3580 to book an appointment.

Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.

References

What is Glaucoma?
https://glaucoma.org.au/what-is-glaucoma/

The Pathophysiology and Treatment of Glaucoma.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4523637/

Glaucoma.
https://www.mayoclinic.org/diseases-conditions/glaucoma/symptoms-causes/syc-20372839

Laser Peripheral Iridotomy. Medscape.

https://emedicine.medscape.com/article/1844179-overview