Detection and management of eye disease is increasingly about multi-modal imaging, according to ophthalmologist Dr. Anna Tan.
Dr. Tan was in Australia to talk to retina specialists about Zeiss’ new AngioPlex OCT Angiography. A junior consultant with Singapore National Eye Centre, Singapore’s largest eye hospital that manages over 60 per cent of the country’s patient load, Dr. Tan regularly uses OCTA in conjunction with fluorescein angiogram and Indocyanine Green (ICG) angiogram technologies and says the advantages are numerous.
From a clinical perspective, she said OCTA is useful because it provides important vasculature and structural information from a non-invasive scan. “A traditional angiogram requires an injection of dye… If the blood vessels are leaky, the dye leaks out and causes a white stain. This is useful because it shows you where the vessels are leaking however, it obscures the vessel structure – so you get information about the activity of the disease but you don’t get details about the vessel structure.”
Dr. Tan said OCTA imaging allows her an added aspect to study the outcomes of different treatment modalities, and in doing so, gain an understanding of why a patient is or is not responding to particular treatments. It also allows her to more closely monitor patients and adjust treatment intervals.
“Right now for instance, we treat patients on OCT findings based on fluid / no fluid, exudation / no exudation. What I’m finding, having used OCTA imaging, is that the vascular complex may actually enlarge before the exudation happens – so the vessels change first and then the exudation may follow. The question is then, if you’ve been treating a patient for a while, and you observe that their vessel complex is getting larger, should we instigate treatment before the fluid comes?”
She said over time, as treatment outcomes are validated, and as the technology is finessed, answers to questions like this will become clearer.
From a patient management perspective, Dr. Tan said OCTA was also advantageous because images are quick to acquire, there is no risk of patients going into cardiac arrest due to the fluorescein injection and neither do you have to worry about any allergies associated with any of the dyes. With no needles required, even patients with a needle phobia can be easily monitored.
Dr. Tan said OCTA images also helped with patient education. “It allows me to give my patients a way to understand the disease – there is nothing like being able to show them before and after photos that clearly demonstrate what the treatment has achieved,” she said.
In years to come, Dr. Tan said she expects to see further refinements to the technology, which will enhance image capturing and analysis. “Right now you cannot take a very wide field of view, so to get the peripheral images you need to take multiple images. And because these images are static, you can’t see the vessel structure change over time.
Additionally she said OCTA had a narrow threshold for measuring velocities of fluid movement. “In the future once the threshold is broadened, OCTA imaging will become even more sensitive and capable of detecting whether the flow is slow, medium or high, which will enable us to identify more and different lesions. “What we all need to remember is that no mode of imaging stands on its own, today it’s all about multi modal imaging.
And if what you are looking at is questionable on one imaging modality, you need to compare that finding to all the other imaging modalities. If they all support your findings, then it’s most likely correct. You need to look at OCTA in context of the structural OCT, the conventional angiography, auto-fluorescence, as well as fundus images and your clinical examination. Together these all create the big picture of what it is you’re looking at.
She said imaging companies are working on developing multi-modal single machines – a machine that can take a photo, auto–fluorescence, angiogram, OCTA and OCT all in one machine. “That is the holy grail of machines,” said Dr. Tan.