Retinal fields nonperfusion identified on ultrawide field fluorescein angiography in diabetic eyes

DESIGN
Cross-sectional prospective study.

PURPOSE
To identify retinal fields nonperfusion on ultrawide field (UWF) fluorescein angiography (UWF-FA) and determine its correlation to diabetic retinopathy (DR) severity on UWF photos (UWF-FP) and macular edema on optical coherence tomography (OCT) among eyes with diabetic eye disease.

METHODS
Sixty-nine eyes from 43 patients with diabetes underwent imaging using UWF-FP, UWF-FA and macular OCT. Diabetic retinopathy (DR) severity was assessed by a masked trained grader on UWF-FP using the international DR classification. UWF-FA images were segmented into ETDRS and 5 extended peripheral (P) fields. Ischemic areas were identified on UWF-FA using Image J (Fiji) software and the nonperfusion index (NPI), cones NPI (CPI) and rods NPI (RPI) within ETDRS and per peripheral field were calculated. The presence of center-involving macular edema (ciDME) was evaluated using spectral domain OCT. Pearson correlation values (r) between UWF and OCT findings were calculated.

RESULTS
Increasing DR severity was correlated with increase in NPI: macular (r = 0.40597, p = 0.0011), within ETDRS (r = 0.50349, p < 0.001), P3 (r = 0.37752, p = 0.0025), P4 (r = 0.43884, p = 0.0004), P5 (r = 0.57411, p < 0.0001), P6 (r = 0.47896, p < 0.0001), P7 (r = 0.55364, p < 0.0001). This remained significant even after distinguishing between cones [CPI: macular (r = 0.42368, p = 0.0006), within ETDRS (r = 0.49783, p < 0.0001), P3 (r = 0.43379, p = 0.0004), P4 (r = 0.45817, p = 0.0002), P5 (r = 0.59082, p < 0.0001), P6 (r = 0.44896, p = 0.0003), P7 (r = 0.55273, p < 0.0001)] and rods [RPI: macular (r = 0.39798, p = 0.0014), within ETDRS (r = 0.49339, p < 0.0001), P3 (r = 0.44759, p = 0.003), P4 (r = 0.45979, p0.0002), P5 (r = 0.59311, p < 0.0001), P6 (r = 0.43911, p < 0.0004), P7 (r = 0.55348, p < 0.0001)]. The presence of ciDME on OCT is correlated with increasing NPI: macular (r = 0.51318, p < 0.0001), within ETDRS (r = 0.53196, p < 0.0001), P6 (r = 0.44692, p = 0.0003), P7 (r = 0.42262, p0.0006); CPI: macular (r = 0.51924, p < 0.0001), within ETDRS (r = 0.54334, p < 0.0001), P6 (r = 0.48529, p < 0.0001), P7 (r = 0.48359, p < 0.0001); and RPI: macular (r = 0.5082, p < 0.0001), within ETDRS (r = 0.53388, p < 0.0001), P6 (r = 0.4813, p < 0.0001), P7 (r = 0.4944, p < 0.0001).

CONCLUSIONS
Retinal nonperfusion is associated with DR severity and ciDME. Our findings suggest that distinguishing between cones and rods nonperfusion may be inconsequential in a generalized retinal disease such as DR. Subfield nonperfusion, especially in the nasal fields (P6 and P7), needs further investigation to elucidate the possible anatomic and functional mechanisms behind its correlation to macular edema.