Diabetic Retinopathy Grading

Retinal status was recorded with a fundus photograph with seven 30° fields (Canon, Lake Success, NY, USA) with pupil dilated. The photographs were evaluated by an experienced ophthalmologist (Wei WW). Another ophthalmologist (Zhu WL) would reassess the photos in case of any doubt. The retinopathy severity was graded according to the ETDRS standard classification[23]. Retinopathy was considered present if there was at least one microaneurysm. The eyes were divided into 2 groups: no DR (NDR, level 10) or any DR (level 20 and above). The DR group was further graded into mild NPDR (20≤ETDRS level<43) and moderate NPDR (43≤ ETDRS level<53).

DME was diagnosed and excluded through stereoscopic biomicroscopy in accordance with the criteria reported by ETDRS, and was confirmed on spectral-domain optical coherence tomography (SD-OCT).