Quantification of retinal microvascular parameters by severity of diabetic retinopathy using wide-field swept-source optical coherence tomography angiography

Purpose: To investigate the diagnostic utility of microvascular parameters for grading the severity of diabetic retinopathy (DR) with a range of views using wide-field swept-source optical coherence tomography angiography (SS-OCTA). Methods: This retrospective study grouped 235 eyes with diabetes into the five grades: diabetes without retinopathy (no-DR), mild non-proliferative DR (NPDR), moderate NPDR, severe NPDR, and proliferative DR (PDR). Foveal avascular zone (FAZ) metrics, vessel density (VD), and the capillary nonperfusion area (NPA) were quantified with a customized, semiautomatic software algorithm. Regions of interest were selected from three rectangular fields of different sizes (i.e., 3 × 3 mm², 6 × 6 mm², and 10 × 10 mm²), perpendicular to the fovea-optic disc axis. Results: NPA obtained from the 6 × 6mm² and 10 × 10mm² areas was the only discriminating parameter for the three NPDR stages. ROC curve analysis revealed that NPA from the 10 × 10mm² field exhibited the best performance for grading DR into five stages. The NPA cutoff values were 3.7% (area under the curve (AUC): 0.91), 4.7% (AUC: 0.94), 9.3% (AUC: 0.94), and 21.4% (AUC: 0.90) for grading no-DR, mild from moderate NPDR, moderate from severe NPDR, and severe NPDR from PDR, respectively. Conclusions: Increasing DR severity as assessed by conventional grading systems is accompanied with increasing retinal ischemia on SS-OCTA. NPA measured from the larger 10 × 10 mm² scan area showed the highest sensitivity for determining five-grade DR severity. In the future, the addition of quantitative NPA may provide a more clinically feasible DR grading system. [Figure not available: see fulltext.]