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Tuesday, 18 September 2018

What is OCT? And do you need it?

A retinal scan using OCT, with a fluid pocket (the black circles within the layers of coloured sensory retina).


OCT, the newest technology to sweep the optical industry. Without any invasive techniques or instruments, a simple scan done alongside your routine eye exam could potentially save your sight.

What does it show?
When our optometrists examine your eyes, they look into them through the pupil. Sometimes, if a patient has small pupils they are dilated, to give a wider view inside. Looking directly onto the retina, your eye health is assessed to look for changes that are or could affect your vision.

With the OCT, we are able to see a cross section through your eye. As if coming through from the side, the scan shows any leakage from blood vessels, haemorrhages. Debris building up in the macular, your area for central vision, reading and recognising faces, also known as age-related macular degeneration. The scan gives an objective measurement of structures in the eye, giving us a 3D model.

Normal Anterior Chamber angle. The top curve is the cornea, which is the front of the eye. The bottom bumpy curve, is the iris, the coloured part of your eye. 

A narrow anterior chamber angle, which could be at risk of closing. 

Newer attachments have allowed imaging of the front of the eye too. Viewing the angle made between the iris and cornea, allows assessment for Glaucoma. The corner of this angle is likened to a drain plug, where fluid created in the eye is drained away. There are some natural iris variations, which look open when viewed from the front, but with scanning can show exactly how wide and open the drainage is. 


How does it work?
It uses scanning lasers, with high depth resolution and high speed acquisition. In a similar way as ultrasound, lots of individual sections are combined to create a 3D image. The OCT sends a optical signal, similar to a light source, into the eye and measures the time taken for the reflection to return. Different structures in the eye, reflect the signal at different lengths.

A technician will position you onto the chin and forehead rest, with your eye comfortably aligned, different scans will be taken. The process takes around 10 minutes to complete. An optometrist will review your scans and relay the results to you.

Both images were captured using an OCT, the left image is how the practitioner sees the eye, when looking through. The image on the right, shows this same area as a cross section. 

Why is it important?
Often changes can happen within the eye, that we are not aware of. The OCT can measure structures that are translucent or lying beneath the surface of the retina. Before we can see and you can feel the changes, the scan will be able to detect them. Using this information, our Optometrists can advice you on the best way to proceed. In the case of AMD, taking a specific formulation of supplements can help to slow down the degenerative process. Though this only has an affect in the early stages of the condition. So the earlier we are able to detect changes, the sooner we can manage them.

So, do I need one?
It is always a good idea to have at least baseline readings that can be compared to at subsequent visits. If there happen to be any changes or new occurrences  that need referencing. OCT scans are recommended for all our patients over 60. The frequency of scanning year after year, is dependent on any monitoring that is required. For some patients, ever other year is sufficient, others will need more regular check ups.

You can find more information on OCTs on our website. We also have an informational leaflet with a home monitoring Amsler grid at our clinics. All of our practices have the Zeiss Cirrus HD-OCTs, call us to arrange an your OCT scan.