Microaneurysm detection using high‐speed megahertz optical coherence tomography angiography in advanced diabetic retinopathy

Abstract Purpose To compare detection rates of microaneurysms (MAs) on high‐speed megahertz optical coherence tomography angiography (MHz‐OCTA), fluorescein angiography (FA) and colour fundus photography (CF) in patients with diabetic retinopathy (DR). Methods For this exploratory cross‐sectional study, MHz‐OCTA data were acquired with a swept‐source OCT prototype (A‐scan rate: 1.7 MHz), and FA and CF imaging was performed using Optos® California. MA count was manually evaluated on en face MHz‐OCTA/FA/CF images within an extended ETDRS grid. Detectability of MAs visible on FA images was evaluated on corresponding MHz‐OCTA and CF images. MA distribution and leakage were correlated with detectability on OCTA and CF imaging. Results 47 eyes with severe DR ( n = 12) and proliferative DR ( n = 35) were included. MHz‐OCTA and CF imaging detected on average 56% and 36% of MAs, respectively. MHz‐OCTA detection rate was significantly higher than CF ( p < 0.01). The combination of MHz‐OCTA and CF leads to an increased detection rate of 70%. There was no statistically significant association between leakage and MA detectability on OCTA ( p = 0.13). For CF, the odds of detecting leaking MAs were significantly lower than non‐leaking MAs ( p = 0.012). Using MHz‐OCTA, detection of MAs outside the ETDRS grid was less likely than MAs located within the ETDRS grid (outer ring, p < 0.01; inner ring, p = 0.028). No statistically significant difference between rings was observed for CF measurements. Conclusions More MAs were detected on MHz‐OCTA than on CF imaging. Detection rate was lower for MAs located outside the macular region with MHz‐OCTA and for leaking MAs with CF imaging. Combining both non‐invasive modalities can improve MA detection.