Optical Coherence Tomography (OCT Imaging)
OCT Imaging is a technique used for obtaining a detailed image of the retina and the multiple layers underneath. This is not possible with the standard eye examination which only allows us to view the surface of the retina. This is important because many eye diseases often begin within or underneath the retina.
It is effectively an ‘optical ultrasound’, using imagine reflections from within the eye using light waves to provide cross-sectional images. OCT provides more information than other imaging methods such as ultrasound or MRI.
- Early detection of a variety of eye diseases. This results in a significantly better chance of retaining your vision as compared to detection at a normal eye exam.
- Non-invasive with no eye contact*
- No radiation
Should I have an OCT scan and how often?
We recommend everyone, including those with healthy eyes, to have an OCT scan performed. This will establish a baseline, so when your eyes start to change in the future, we can compare what has changed and by how much.
After performing a baseline OCT, we recommend OCT imaging every three years with your standard eye test. However if you are over 40 years old or are experiencing any eyesight problems, a yearly scan is preferable. The images are stored electronically, so regular OCT imaging helps us to build a clear picture of your eye health over time. By comparing records, it’s easier to identify subtle changes that may indicate the early signs of disease.
Specific indications to perform an OCT scan include:
- Patients with unexplained vision deterioration
- Abnormality detected at the back of the eye during a routine eye examination
- Abnormality detected during a retinal photography scan
- Patients with diabetes (who have an increased risk of developing retinal disease)
- Patients with a family history or other increased risk of developing macular disease** or glaucoma^
- Patients with high intra-ocular pressure
- Patients with visual field loss
- Evaluation of corneal conditions and anterior chamber depth
** The macula is a specialised area of the retina responsible for the detailed vision necessary for everyday tasks such as reading and recognising a person’s face. An OCT scan is usually the best method to detect and monitor a range of macular conditions including macular degeneration, macula traction, epiretinal membrane, macular hole, diabetic retinopathy and oedema.
^ Glaucoma is a disease resulting in damage to the optic nerve (the nerve bundle which connects the eye to the brain). Increased pressure in the eye can lead to damage to the optic nerve. As damaged nerve fibres cannot regenerate, early detection and treatment is vital to prevent further nerve damage. The OCT measures the thickness of the nerve layer around the optic nerve. Efficiency of the drainage system in the front chamber of the eye and thickness of the cornea are also contributing factors to glaucoma. The OCT provides information on these factors.
Visual Field Test
The visual field test is a subjective measure of central and peripheral vision, or “side vision,” The use of visual field test is essential in diagnosing and monitoring glaucoma, or any vision loss as a result of damage to the visual pathways of the brain or other optic nerve diseases. It uses a light flashes that is repeatedly presented in different areas of your peripheral vision. A visual field test is performed as soon as glaucoma is suspected, and the visual field data is used to determine the severity of disease. This staging information is useful in determining follow-up and/or treatment strategies.
OCT and retinal photograph imaging of the optic nerve and surrounding tissues is an objective test that can also detect glaucoma damage and progression. However, at this time it has not replaced the visual field test. We still need both types of testing because there are times that the optic nerve changes before the visual field, but also times when changes to the visual field are observed before damage to the optic nerve is detected.
Digital Retinal Photography
Digital Retinal photography is used to examine and monitor the health of your retina, optic nerve and blood vessels. As such it is well complemented with OCT imaging which enables us to grasp a better picture of what’s happening under the surface of your eye. Digital retinal photography provides the benefits of early detection of eye conditions including:
- Macular degeneration
- Retinal changes associated with diabetes
- ‘Moles’ on your retina. Just like any other moles on your body, these should be checked regularly to make sure there are no changes.
Oculus Keratograph 5 (K5)
This machine has revolutionised Dry Eye assessment. The K5 allows us to have an in-depth look at the eyelid anatomy and tear film to diagnose and manage dry eyes quickly and accurately. It allows us to scan and measure critical features such as:
- The quantity of tears,
- The quality of lipids in tears,
- Tear break-up time,
- The integrity of the Meibomian Glands.
The K5 has the following features:
- Meibo-scan allows us to see the structural changes of the glands
- TF-scan uses infra-red illumination to assess the quality and quantity of the tear film.
- Infra-red illumination evaluates the tear film.
- Lipid layer thickness which directly links to tear evaporation and dry eye symptoms. If the lipid layer is too thin or absent, the tear evaporation rate and the tear film instability increases.
- R-scan is the first and only technology that objectively measures and classifies the degree of redness in blood vessels.
A corneal topographer is a non-invasive instrument which maps the curvature of the cornea and outer-part of the eye. Corneal topography is essential in allowing optometrists to fit custom contact lenses and diagnose eye conditions such as keratoconus, Terrien’s marginal degeneration, or monitor pterygium.