Optical Coherence Tomography (OCT) is a non-invasive imaging technique that allows eye care professionals to measure the thickness and health of your retina’s multiple layers. It’s cutting-edge technology that allows optometrists to detect signs of glaucoma, among other serious eye conditions.
OCT gives optometrists a better ability to detect and monitor minute changes in the retina and optic nerve than is possible through a standard eye test alone. Typically, signs of glaucoma can be detected up to 4 years earlier with OCT than with traditional imaging methods.
You may not have heard of OCT before, so here we’ll explain what an OCT scan does and how it can be used to detect glaucoma.
Glaucoma is a disease that can creep up on you without any signs or symptoms. In fact, for many people, glaucoma is caused by a painless rise in pressure inside the eye. This is called ocular hypertension.
This rise in pressure can cause gradual but irreversible damage to nerve fibres and may lead to tunnel vision if left untreated.1 Fortunately, there are treatment options for glaucoma, and the earlier it’s picked up the better.
Early detection means that treatment with prescribed eye drops, laser treatment or surgery can be started before you experience any significant sight loss — and an OCT scan is a key way to detect any early changes.
Much like an ultrasound scan uses sound waves, OCT uses light waves to take thousands of images of your retina, the layer of nerve fibres at the back of the eye.
In order to carry out an OCT scan, you’ll be asked to sit with your chin on a support in front of a compact machine. The equipment will scan your eye without touching it. You will need to look at a light inside the machine and you may see a flash of light.
The test is then repeated on the second eye. Overall, scanning takes a few minutes and is completely painless. You may feel a little dazzled for a few moments after the test but this will quickly settle down — this is completely normal and similar to having your photo taken with a bright camera flash.
The OCT scan creates an image of each of the retina’s layers which can then be mapped and measured. While your first OCT scan can pick up signs of glaucoma, for most people this first test will set baseline data when your eye is healthy. The clever thing about OCT is that it can pick up subtle changes in the thickness of the nerve fibre layers over time, giving your optometrist information which may indicate very early signs of conditions like glaucoma. By repeating the OCT scan at every eye test your optometrist can see if the nerve fibre thickness is changing outside of the normal age-related levels, and take action if it is.
The optic nerve head is visible at the back of your eye and it’s from here that all the nerve fibres across the retina radiate. This important structure is affected by glaucoma and, as such, an OCT scan is used to specifically evaluate disorders of the optic nerve. This type of scan is extremely valuable to optometrists as it allows them to get a comprehensive picture of your eye health.
Your optometrist will use information from an OCT scan alongside measurements of the pressure inside your eye, your visual fields, and an evaluation of the appearance of the back of the eye before concluding there are signs of any glaucoma, or any other eye disease.
If there are any signs you will be referred to a specialist eye doctor, known as an ophthalmologist, who would formally diagnose you with glaucoma and go through the options for treating glaucoma and how they will help you manage it.
The most important thing to remember is that the earlier glaucoma is found, the better chance there is for treatment to help prevent sight loss.
By assessing the nerve fibres at the back of your eye at an early stage, an OCT scan can pick up small changes, and onward referral means you can receive the right treatment. This technology is an incredibly important development which could reduce the risk of sight loss due to conditions like glaucoma for everyone in the future.
OCT is currently available in a select number of Specsavers stores. You can find your nearest store here.
For more information on how glaucoma is detected and diagnosed, you can find it in our dedicated glaucoma diagnosis resource.
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1. http://www.glaucoma-association.com/about-glaucoma/types-of-glaucoma/chronic-glaucoma accessed 09/05/2019
BSc (Hons) MCOptom Prof Cert Glauc. Prof Cert Med Ret.
Ross is an experienced optometrist, pre-registration optometrist supervisor, and lead assessor for the Wales Optometry Postgraduate Education Centre (WOPEC)… Read more