The “I”s Have It: What Imaging is Now Able to Tell Us

One of the things I thought before heading to New Orleans was that there were an impressive number of presentations on optical coherence tomography angiography (OCTA). It got a lot attention at the American Academy of Ophthalmology because it should – we have learned a lot about this exciting technology but much remains to be elucidated before its full clinical potential can be realized

Phil Rosenfeld, MD delivered an excellent talk at Retina Subspecialty Day about visualizing non-exudative neovascular age-related macular degeneration (AMD) using OCTA. 

These are eyes without intraretinal or subretinal fluid with the presence of a choroidal neovascularization membrane (CNVM), identified by OCTA. Phil Rosenfeld, MD, has correlated the presence of these areas with indocyanine green (ICG) angiography, showing that there are CNV lesions that “lurk” beneath the retinal pigment epithelium (RPE), often in the form of a shallow, dense, sometimes irregular pigment epithelial defect, in the configuration of type 1 CNVM. Right now, it’s unclear among retina specialists how we should follow those eyes or treat those eyes.

I agree with Dr. Rosenfeld’s approach, and I’ve implemented it in my practice. He basically advises that if we find these lesions at a non-exudative stage, there is no data to indicate the lesions should be actively treated with anti-VEGF intravitreal injections. I do recommend following these eyes more closely because of the possibility that these clinically quiescent lesions can convert into an exudative situation requiring intervention. 

Another angle of OCTA is to evaluate the native retinal vascular bed in the setting of retinal vascular diseases. Progressive retinal nonpefusion is a hallmark of both diabetic retinopathy and retinal venous occlusive diseases and it appears that anti-VEGF therapy can change the trajectory of non-perfusion by significantly slowing the development and progression of the loss of normal retinal perfusion. OCTA is providing a new tool to better analyze the impact of our pharmaceuticals as well as the underlying disease process itself. Richard Rosen, MD, also presented elegant imaging using adaptive optics of changes in perfusion status over time. 

Finally, while I think the insights we are gleaning from OCTA are exciting and informative, there was a pro-con debate during AAO that asked the audience if OCTA was essential for clinical practice. While both sides had good points, most attendees voted that OCTA is not ready for mainstream clinical retina.

For the time being, I think OCTA has a proven and expanding place within clinical research. But, it may take a while before we see it as “necessary” in our day-to-day clinical settings. I think the analytical software used in the clinic needs to improve. Doctors simply don't have enough time to fiddle with the multiple segmentation options of current-generation software during a busy clinic. 

My last take on imaging has to do with ultra-widefield. I have adopted it in my practice for evaluating retinal vascular disease. It has changed my management approaches with these patients, and now there’s data that the information from the periphery - for example the number of physical lesions compared to lesions more posteriorly - in diabetic retinopathy can be informative for prognostication. Specifically, eyes with a distribution of predominately peripheral lesions, or “PPLs,” are at higher risk of conversion to proliferative diabetic retinopathy, an important clinical transition.

I have no doubt we’ll be hearing more about PPLs. Protocol AA from the Diabetic Retinopathy Clinical Research Network is going to be a key trial in helping better define the role of ultra-widefield imaging in clinical practice.. 

- Charles Wykoff, MD