Author: Daniel Hardiman-McCartney MCOptom, Clinical Adviser and Martin Cordiner, Head of Research
Date: 23 January 2017
New technologies are exciting, but it is important to stay focused on how any new technology may improve your clinical practice and commercial offering and perhaps most importantly, what it will mean to your patients. To help you get the most out of the upcoming Optometry Tomorrow 2017 (OT17) sessions here is a little background to the new technology of optical coherence tomography angiography. Currently there is only limited published research describing the power of this new technique to improve clinical outcomes or make earlier and more accurate diagnosis, but the evidence base is growing. Over the next couple of years OCT-A will be an evolving field and more case studies and trials investigating the performance will be published. The sessions at OT17 will give you a head start to understanding the potential and what to look out for in the future. Will the theory and marketing claims match the reality when tested both in the lab and clinic?
OCT-A is non-invasive as no fluorescein dye is needed, making it safer, quicker and easier to perform without the unpleasant side effects.
What is OCT-A? Optical coherence tomography angiography, or OCT-A for short, is a way of imaging micro-vascular blood vessels and blood flow in the retina and choroid by analysing OCT information. Ultimately it works by clever maths: by comparing the data from several OCT scans captured at the same location taken at high speed, successively. Motion contrast changes are calculated and extracted from the image data and are used to create a characterisation of both the structure and function/flow of the retinal vasculature, including the choridal capillaries.
Is this the same as Fluorescein angiography (FA)? OCT-A is not the same as FA and nor is it an overnight replacement for it. Both imaging techniques result in valuable microvascular information and OCT-A has some advantages over FA in that it enables visualisation of distinct vascular networks at a much higher resolution than FA. However, with OCT-A, leakage and very slow flow information are not well visualised. As such FA remains an important tool for evaluating patients in the first instance and for the foreseeable future continues to be vital for the differential diagnosis of retinal pathology due to the invaluable retinal leakage and perfusion information.
What are the potential benefits to my patients of OCT-A? FA requires intravenous administration of fluorescein dye, limiting the technique to hospital clinics and although safe, is not without unpleasant side effects and in rare instances can result in anaphylaxis. OCT-A on the other hand is non-invasive as no fluorescein dye is needed, making it safer, quicker and easier to perform without the unpleasant side effects. It can be easily repeated at follow up appointments and those appointments could be in an optometric practice, ideal for practices with an interest in medical retina or part of an AMD shared care pathway.
What could the future hold for OCT-A? Experts agree OCT-A offers great diagnostic potential for retinal pathology and is a useful addition to traditional OCT, although more research and long term follow ups are required to be able to fully understand and rely on the technology. There is potential scope for the technology to assess optic nerve head blood flow in glaucoma. In the long term there is also the possibility the technology could be refined to reduce the number of initial fluorescein angiograms required.
What do I need to do in order to offer OCT-A in practice? If you already have an OCT, in theory a software update may be all that is needed. However it is likely you will need to replace your whole OCT if you want to be able to offer OCT-A, as the analysis software relies on your instrument scanning at the highest speed and resolution and so is not compatible with earlier generations of OCT. As with all new technologies, the equipment is only part of the investment: resources should also be set aside for training and team development, as interpreting the visualizations and 3D images will require skill and practice. Carl Zeiss, Heidelberg Engineering and Topcon will be demonstrating their OCT-A technology at OT17.
Do I need OCT-A? The best way to know would be to attend the sessions at OT17, hear what our speakers have to say about the latest research, what to look out for and learn how other practitioners are already using OCT-A in their practices. When adopting any new diagnostic technology, there is always a learning curve and a case of collective discovery about which parts of the newly available data are clinically useful. Many will remember the discussion about hyper-reflective dots in the early days of OCT as a case in point. Whether it is right for your practice is a question only you can answer, but for those with an interest in providing AMD shared care, it may be only a matter of time before you will be using this technique.
Optometry Tomorrow 2017 sessions
Sunday 10:40: OCT angiography in practice lecture by Tomas Burke, Bristol Eye Hospital
Monday 10:05: OCT Interpretation and angiography by Clare Bailey
Monday 9:00: Topcon: New frontiers with OCT angiography