How is glaucoma detected?
How is glaucoma detected?
Glaucoma, known as the sneak thief of sight, is a progressive disorder of the optic nerve, related to genes, age and a variety of environmental factors.
In glaucoma, the optic nerve at the back of the eye accumulates damage over time, and loses function in a piecemeal fashion. This results in the painless progressive reduction in vision – tending to affect peripheral vision prior to central vision.
Glaucoma sneaks up on eyes over time. Because we only tend to notice vision loss once it reaches our central vision, and because one eye can compensate for the other, we often don’t notice glaucoma damage until it is relatively advanced.
Early detection is critical to successful glaucoma treatment and saving sight; if detected early, we can intervene in the natural history of glaucoma by lowering the eye pressure and alleviating other modifiable risk factors.
Testing for glaucoma
Glaucoma is most commonly detected during a regular eye check with an Optometrist. With many Optometry practices available to access, it is important for us all to have our eyes checked regularly. As well as checking that our spectacles are correct for us, this gives an opportunity for screening of common eye conditions, such as glaucoma.
Admittedly, most major eye problems tend to become more common with increasing age, but glaucoma can begin in early middle age and even in some cases children or adolescents.
Currently, Australians aged 50 and over are recommended to have a screening eye exam with an Optometrist or Ophthalmologist at least every 2 years. People with additional risk factors (such as a family history of glaucoma, previous eye trauma, short-sightedness or long-sightedness, or diabetes) should start screening at an earlier age.
If an Optometrist detects signs suspicious for glaucoma when examining our eyes, further testing and referral to a subspecialist Ophthalmologist generally occurs before glaucoma treatment is discussed.
Here are the tests most frequently performed to diagnose glaucoma:
Optic nerve examination
The critical changes of glaucoma occur at the optic nerve and that is where it is most commonly detected. When an Optometrist or Ophthalmologist examines our eyes, they carefully study the optic nerve for signs of glaucoma, by looking through our pupils and examining the optic nerve at the back of the eye. Thinning of the optic nerve rim or bleeding around the nerve are signs of glaucoma.
Intraocular pressure (IOP) is important for assessing glaucoma risk, but is not necessarily diagnostic for glaucoma. It should be remembered that many people who have glaucoma have normal IOP, and many people have high IOP but no glaucoma. However, high IOP is often a clue that glaucoma might be occurring, and is often associated with glaucoma.
A scan of the optic nerve using Optical Coherence Tomography (OCT) is important to provide a more detailed analysis of the optic nerve. Often early signs of glaucoma are detected on an OCT which are not necessarily visible on examination of the optic nerve. OCT scans are increasingly common and perfectly safe for eyes.
Visual field test
We are often unaware of minor changes in our peripheral vision – that is why it needs to be carefully checked. Visual field testing involves asking us to focus our gaze on a central point, and shining lights at different brightness at locations in our peripheral vision. The idea is to generate a map of our visual sensitivity at all locations and see if there are any deficits. Once glaucoma has been detected, serial visual field testing is the best way to monitor for change over time.