Evaluation of diabetic retinopathy severity on ultrawide field colour images compared with ultrawide fluorescein angiograms

Purpose To compare Early Treatment Diabetic Retinopathy Study (ETDRS) diabetic retinopathy (DR) severity on ultrawide field (UWF) colour imaging (CI) and UWF fluorescein angiography (FA). Design Cross-sectional retrospective review. Subjects Patients with diabetes mellitus and at least mild non-proliferative DR on UWF-CI. Methods UWF-CI and UWF-FA images acquired within 1 month of each other were evaluated independently using ETDRS DR Severity Scale (DRSS) for colour photography adapted for UWF-CI and UWF-FA. Extent of non-perfusion (NP, mm 2) was determined from UWF-FA images. Main outcome measures Agreement rate between DRSS on UWF-CI and UWF-FA. Results Images from 218 eyes of 137 patients with diabetes were evaluated. Agreement rate for DRSS between UWF-CI and UWF-FA was moderate to substantial (K=0.46, Kw=0.65). Over-all, DRSS was worse in 73 (33.5%) eyes on UWF-FA and in 16 (7.3%) on UWF-CI. Compared to UWF-CI, UWF-FA identified more severe DRSS in 26.5% (1 step) and 7.34% (≥2 steps) of eyes. DRSS was worse than UWF-FA in 56 (51.4%) in early DR (ETDRS levels 20-47, N=109) and 17 (15.6%) in eyes with severe DR (53 and higher, N=109). In this cohort, the extent of NP significantly increased as eyes approach moderate non-proliferative DR (levels 43-47, p=0.0065). Conclusion When evaluating UWF-FA images using the ETDRS colour severity scale, DRSS is graded as more severe in a substantial number of eyes than when evaluating UWF-CI. It is uncertain how the DRSS levels using UWF-FA translate to clinical outcomes, but the additional lesions detected might provide added prognostic value. These and other recent data emphasise the need of obtaining outcome data based on UWF-FA and the potential need to develop DRSS specifically tailored for UWF-FA images.