What Is an OCT Scan?

An Optical Coherence Tomography Scan, more commonly known as an OCT scan, is a medical imaging technique that uses light to generate a detailed three-dimensional view of the different layers of your eye. It is a fast, completely painless, and incredibly accurate way for our specialists to see beyond the surface of your eye. Just like a CT scan allows doctors to see a 3D view of the inside of your body, an OCT allows our optometrists to examine every layer of your eyes, in very fine detail. Which then, in turn, assists in diagnosing a multitude of eye conditions at the earliest possible stage.

Common eye diseases can creep up on us, without any symptoms. Some eye diseases can cause irreversible sight loss. So, it is important to detect any subtle changes at the back of the eye. Even if your vision and eyes are perfectly fine, it is useful for your Optometrist to gain a full understanding of your overall eye health through supplementary tests. An OCT scan can help your Optometrist understand what is going on beneath the surface of your eye.

The picture is precisely created by measuring the amount of dim red light (like how an ultrasound scan uses sound waves) that reflects off the retina. By attending multiple OCT scans over the years, your Optometrist can notice slight changes in the thickness of the layers of your retina. This can indicate early signs of eye conditions, making it much easier to diagnose, treat and manage.

What Happens During an OCT?

The SPECTRALIS 4D OCT Scan is fast, non-intrusive, and does not present a bright flash of light or a puff of air. You simply sit down, pop your chin on the chin rest, and the eye is scanned in just a few seconds. You can blink normally, and as nothing touches your eye, there is no discomfort. Following the scan, your optometrist will then discuss your results, showing you the images whilst clearly explaining their findings.

What Conditions Does an OCT Scan Help to Diagnose?

The SPECTRALIS OCT scanner assists our specialist optometrists in detecting and diagnosing a multitude of eye conditions at the earliest possible stage. It is also ideal for the management and maintenance of pre-existing eye conditions, such as glaucoma and age-related macular degeneration (AMD).

Glaucoma

Often called “the thief of sight”, glaucoma is a hereditary disease that affects your peripheral vision. One in two people with glaucoma don’t even know they have the disease until it has reached an advanced, and irreversible, stage. This is because your brain compensates for the blind spots in your vision by filling in the gaps. Unfortunately, this results in either ‘seeing things’ that are not there or missing the things that actually are.

Age-Related Macular Degeneration (AMD)

AMD is the biggest cause of sight loss in the UK, affecting over 600,000 people. AMD affects your central vision and comes in different forms that have various symptoms and different rates of progression. If AMD progresses, simple activities like driving, watching TV, and even recognising faces become impossible. SPECTRALIS OCT scans allow our specialist optometrists to detect and monitor any change and help limit the severity of the disease.

Diabetic Retinopathy

Diabetes is a serious disease that can cause irreversible sight loss. When blood sugar levels are poorly controlled, the blood vessels of the eye become damaged, causing them to leak fluid; this is known as diabetic retinopathy. Regular SPECTRALIS OCT scans allow us to detect any fluid or damage to blood vessels as soon as it starts.

Cataracts

Research shows that by the age of 60, half of us will have some degree of cataract, resulting in the clouding of the lens, a reduction in clarity, and impaired colour definition.

SPECTRALIS OCT scans allow our optometrists to monitor both the development of the cataract as well as the measurement of contrast sensitivity function. A far more useful measure of visual function in cataracts.

Are All Oct Scans the Same? 

Not all OCT machines are the same. There are two main types of OCT machines

1.     Time-domain OCT

2.     Fourier-domain OCT

At the Eye Academy, we utilise the Heidelberg Spectralis HRA+OCT machine. This hospital-grade device allows for different imaging modalities including spectral-domain OCT, fundus autofluorescence, red-free and infrared photography. This device has a scanning speed of 40,000 scans per second, which provides the clearest image when compared to any other OCT machine. The Spectralis has a dual-beam scanning system and eye-tracking technology that recognises any eye movement. This creates a comfortable experience as well as creating a clear scan. This is because the OCT machine repositions the scan if it detects any eye movement and discards scans with any artefacts caused by eye movement. The Spectralis detects specific structures in the eye and allows for automatic rescanning of the retina at the same location as the previous visit. This allows your Optometrist to compare exact parts of the retina.

What Are The Different OCT Scans Used For?

Spectral Domain OCT

OCT uses light waves to take cross-section pictures of your retina. With OCT, your Optometrist can see each of the retina’s distinctive layers. This allows your Optometrist to measure the thickness of each retinal layer. These measurements help with diagnosis. OCT machines also provide treatment guidance for glaucoma and diseases of the retina. These retinal diseases include age-related macular degeneration (AMD) and diabetic eye disease.

Fundus autofluorescence

Fundus autofluorescence (FAF) is a non-invasive retinal imaging modality used in clinical practice to provide a density map of lipofuscin. This modality of imaging is particularly useful with people who have conditions such as age-related macular degeneration, Retinitis pigmentosa, Stargardt disease, Best disease and various maculopathies. FAF is also used during a Hydrochloroquine retinopathy screening.

Red-free Photography

Red-free fundus photography is the standard method of assessing glaucomatous damage to the retinal nerve fibre layer and determining the progression of glaucoma.

Who Should Have an OCT Scan?

Ideally, every patient should have this test on every visit as it is the most precise, most accurate way to see any changes in the eye no matter how small. But for those who have been diagnosed or have a family history of eye conditions; this is an essential part of your health check as it can reveal changes in the eye of which you may be unaware. Perfect vision does not mean perfect eye health. Many conditions remain hidden until it is too late, and you begin having vision problems. If problems with your vision arise, this can often mean that significant damage to your eye has already occurred, and this damage may be irreversible. Including a SPECTRALIS OCT scan in your eye examination assists in early detection, therefore, allowing for early treatment and a better outcome for patients.