Background/Objectives: Discrepancies in diabetic retinopathy (DR) grading are well-documented, with retinal non-perfusion (RNP) quantification posing greater challenges. This study assessed intergrader agreement in DR evaluation, focusing on qualitative severity grading and quantitative RNP measurement. We aimed to improve agreement through structured consensus meetings. Methods: A retrospective analysis of 100 comparisons from 50 eyes (36 patients) was conducted. Two paired medical retina fellows graded ultra-widefield color fundus photographs (CFP) and fundus fluorescein angiography (FFA) images. CFP assessments included DR severity using the International Clinical Diabetic Retinopathy (ICDR) grading system, DR Severity Scale (DRSS), and predominantly peripheral lesions (PPL). FFA-based RNP was defined as capillary loss with grayscale matching the foveal avascular zone. Weekly adjudication by a senior specialist resolved discrepancies. Intergrader agreement was evaluated using Cohen’s kappa (qualitative DRSS) and intraclass correlation coefficients (ICC) (quantitative RNP). Bland–Altman analysis assessed bias and variability. Results: After eight consensus meetings, CFP grading agreement improved to excellent: kappa = 91% (ICDR DR severity), 89% (DRSS), and 89% (PPL). FFA-based PPL agreement reached 100%. For RNP, the non-perfusion index (NPI) showed moderate overall ICC (0.49), with regional ICCs ranging from 0.40 to 0.57 (highest in the nasal region, ICC = 0.57). Bland–Altman analysis revealed a mean NPI difference of 0.12 (limits: −0.11 to 0.35), indicating acceptable variability despite outliers. Conclusions: Structured consensus training achieved excellent intergrader agreement for DR severity and PPL grading, supporting the clinical reliability of ultra-widefield imaging. However, RNP measurement variability underscores the need for standardized protocols and automated tools to enhance reproducibility. This process is critical for developing robust AI-based screening systems.

Background/aims To characterise the distribution of retinal non-perfusion and its relationship with neovascularisation elsewhere (NVE) and visual acuity (VA) in referable diabetic retinopathy (DR) using ultra-widefield fluorescein angiography (UWFA). Methods Eyes with treatment-naïve moderately severe non-proliferative DR (NPDR) to proliferative diabetic retinopathy (PDR) (Diabetic Retinopathy Severity Scale (DRSS) level 43–60) with available UWFA were included in this study. Total and zonal non-perfusion and NVE area were manually delineated across concentric zones (central 1–10 mm, extended posterior >10–20 mm and mid-peripheral >20–30 mm diameter). The Non-Perfusion Index (NPI) was calculated as the ratio of non-perfused area to total area per zone. Associations between NPI, NVE, DR severity and best-recorded VA (BRVA) were assessed. Results A total of 133 eyes (60.9% NPDR, 39.1% PDR) were analysed. The highest NPI occurred in the mid-periphery (20–30 mm) and posterior pole (15–20 mm) zones, with nasal preponderance. NVE was most frequently observed in the posterior pole (66%) and nasal quadrants. Central and mid-peripheral NPI correlated with NVE area in corresponding zones, showing quadrant-specific associations. Receiver operating characteristic analysis identified a total NPI threshold of 0.23 to differentiate PDR from NPDR (area under the curve=0.798), with the lowest threshold in the superior quadrant. Neither NPI nor NVE area correlated with BRVA. Conclusion NVE represents a localised response to adjacent ischaemia predominantly affecting the nasal and extended posterior retina. NPI threshold of 0.23 distinguishes proliferative from non-proliferative stages, with the superior quadrant showing greater susceptibility to NVE at lower ischaemic levels. No significant correlation found between NPI, NVE area and visual acuity.