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OCTA technology

Chris Mody discusses visualising the retinal vasculature

OCT angiography (OCTA) imaging provides unique, non-invasive images of blood flow and high quality images of the retinal vasculature.

The principle at the core of OCTA is that in a static eye the only moving structure is blood flowing within vessels. OCTA is able to differentiate moving cells from other retinal tissue and identify the flow signal through consecutive B-scans, which are displayed as OCTA section images.

OCTA images are susceptible to motion artefacts, so a live eye tracking system is essential to mitigate for this and to make accurate OCTA follow-up scans possible. 

The retina has four distinct vascular plexus with unique morphology to meet the metabolic demands of specific retinal tissues. The average diameter of a retinal capillary is 8 microns, which includes the lumen. The blood flow within a retinal capillary is approximately 6.4 microns in diameter; therefore the lateral resolution of an OCTA system must meet or exceed this minimum specification in order to accurately record capillary flow and blood vessel patterns. The Spectralis OCT Angiography Module achieves a lateral resolution of 5.7 microns and an axial resolution of 3.9 microns per pixel, permitting visualisation of all four vascular plexus and ensuring diagnostic confidence.

"OCTA technology is still in its infancy, with a large amount of research ongoing"

OCTA technology is still in its infancy, with a large amount of research ongoing, so interpretation of the images is currently challenging. However, OCTA has the potential to improve patient care in the community and open up shared care pathways in the future. 

When deciding which OCT device to purchase, technologies that are modular and upgradeable are a wise investment. 

Visit YouTube to view a video on interpreting the normal retinal vasculature of OCTA images.