Nadia K. Waheed, MD, MPH

OCT angiography (OCTA) is a sensitive imaging modality for detecting choroidal neovascularization. However, unlike fluorescein angiography, which can detect and differentiate between active and non-leaking vessels, thus giving clues regarding disease activity, OCTA does not visualize leakage and therefore cannot differentiate whether the subretinal or sub-RPE visualized is quiescent or leaking. Although there are clues to activity based on the appearance of subretinal and intraretinal fluid on structural OCT, there is, so far, no definitive way to identify leaking CNV on OCTA. Identifying activity is important not just from a therapeutic point of view but also to gain a better pathologic understanding of what drives disease activity. Several groups have been working on classifying CNV on OCTA to help better understand which characteristics can be used to predict whether a patient has exudation. Coscas and colleagues published a preliminary classification system that evaluated the characteristics of a CNV on OCTA that correlate with disease activity. Sarraf, in this study, expands on and refines classification of factors that predict activity. In his study, he found that greater fractal dimension, for example, more complex branching of the vessel structure within the CNV, the presence of peripheral arcades with anastomoses and secondary small vessel branching are all biomarkers of activity. Also, absence of peripheral arcades, lower fractal dimension, absence of branching in the secondary vessels and the presence of large straight vessels, a feature that probably indicates chronicity, are associated with disease inactivity. Sarraf’s model seemed to distinguish very well disease activity based on these characteristics. While these results need to be replicated in larger patient cohorts, the results from this study may eventually have a large impact in how we evaluate CNV in clinic.