You may have come across the term “glaucoma” at least once at some point in your life. A parent may have mentioned in passing that an older relative was recently diagnosed with glaucoma, you may have come across the word in the media lately, or perhaps you yourself may have been told that you have a “risk of glaucoma” that requires monitoring. But exactly what is glaucoma, how is it treated, and more importantly, what are the symptoms or signs of glaucoma that could alert you to visit an eye care provider?
The prevalence of glaucoma in Australia sits around 3%; approximately half of those with the disease are actually unaware they have it.
What is Glaucoma?
Glaucoma is a type of eye disease known as an optic neuropathy, referring to damage and disease of the optic nerve at the back of the eye. The optic nerve is a bundle of nerve fibres that carry signals from the sensory retina of the eye to the brain for visual processing – damage to this nerve from glaucoma results in irreversible vision loss. There are a multitude of underlying causes of this disease, and not all of it is yet well understood.
At a basic level, we know that damage to the optic nerve occurs because the pressure inside the eye, intraocular pressure (IOP), is at a level too high for the health of the nerve; there are also likely other factors that reduce the nerve’s tolerance of and resilience to these pressures, such as age, oxidative stress, or specific anatomical characteristics.
Many factors have been associated with glaucoma but the most commonly quoted risk factors include:
- Refractive error, both long- and short-sightedness
- Family history of glaucoma
- Increasing age
- Use of steroidal medication
- High IOP
- Asian ethnicity
- Sleep apnoea
What are the Signs of Glaucoma?
In the vast majority of cases there will be no noticeable symptoms to alert an individual that they may have glaucoma. The vision loss from glaucoma is painless and, as the loss begins in the periphery where we are less aware of such slow changes, once the vision has deteriorated to a point where it does become noticeable, the disease is often already in its advanced stages.
In a sub-type of glaucoma known as acute angle closure glaucoma, the IOP may suddenly spike to very high levels, which has the potential to induce symptoms including blurred vision, haloes around lights, a very red, painful eye, and even nausea and vomiting. However, these presentations are relatively rare and, in most cases, glaucoma goes entirely undetected until you attend for a routine eye exam.
Detecting the signs of glaucoma and coming to a definitive diagnosis are unfortunately not always straightforward. This is due to a variety of reasons, including physiological differences between healthy individuals and even between individuals with the condition, and the fact that glaucoma is a very complex disease.
When examining an eye for glaucoma, tests include:
- Tonometry – this is a method of measuring IOP. Several techniques are available for this, including non-contact tonometry involving an air puff, iCare tonometry using a light probe to tap the surface of the eye, or applanation tonometry, which requires anaesthetic eye drops and a larger probe gently placed on the eye.
- Optical coherence tomography (OCT) – this non-invasive scan provides information about the thickness of the retinal nerve fibre layer and can detect areas of damage and thinning. Certain models of OCT machines can also record and analyse progression of nerve thinning over a series of scans.
- Visual field testing (VFT) – also known as automated perimetry, VFT maps the sensitivity of your vision across the visual field. Areas of damaged retinal nerve fibre will correspond to areas of decreased sensitivity or vision loss in a certain area of the visual field. Studies have shown that up to 50% of the nerve fibre layer can be lost before manifesting on VFT so this test is not often used as the first-line for detecting glaucoma but can be helpful to aid in diagnosis and monitor progression.
- Ophthalmoscopy – by directly looking inside the eye, a trained practitioner can assess the neuroretinal rim of the optic nerve for any changes to its thickness, shape, and colour that may indicate glaucomatous damage.
All treatments involve lowering the IOP in efforts to protect the optic nerve from further damage, but no treatment is able to reverse existing damage or cure glaucoma altogether. Traditional therapy has involved topical eye drops, such as beta-blocker or prostaglandin drugs, which either decrease fluid production in the eye, increase fluid outflow, or a combination of both, to control the IOP.
Laser procedures are also available to stimulate fluid outflow but the effects of these often wear off over a number of years. We now also have the advent of minimally invasive glaucoma surgery (MIGS), which describe the insertion of microscopic stents or tubes into the eye to aid in fluid outflow.
Though many patients are already successfully treated with the existing therapies, glaucoma treatment continues to advance and evolve with greater understanding of what drives this disease.
Protect and maintain your eye health, contact us at 1300 297 583 to schedule a consultation.