Comparison of Ultra-Widefield Imaging and Standard Imaging in Assessment of Early Treatment Diabetic Retinopathy Severity Scale

PURPOSE: To compare Early Treatment Diabetic Retinopathy Study (ETDRS) severity levels between standard 7-field imaging and ultra-widefield (UWF) imaging and to incorporate peripheral diabetic retinopathy (DR) lesions into the ETDRS grading system. DESIGN: Cross-sectional Study. PARTICIPANTS: Paired images from 192 eyes (189 participants) with diabetic retinopathy were included. METHODS: The ETDRS levels were determined by masked graders in 3 ways: standard 7-field imaging, UWF within the 7-field region (7-field UWF imaging), and the entire UWF image (global ETDRS imaging). MAIN OUTCOME MEASURES: Percentage agreement between 7-field and UWF imaging for ETDRS levels. RESULTS: Of the 166 paired images evaluated, exact agreement was found in 48.8% of eyes between standard 7-field and 7-field UWF ETDRS levels with a weighted κ value of 0.59 (95% confidence interval [CI], 0.5–0.68). Agreement rates varied with DR severity and were least in early DR (30.8%) and moderate nonproliferative DR (26.5%) groups. In 156 eyes with 7-field UWF ETDRS and global UWF ETDRS levels, exact agreement was found in 143 eyes (92%), with a weighted κ value of 0.9 (95% CI, 0.9–0.98). The peripheral lesions contributed to a higher DR severity in 8% and changed the eye to a proliferative DR level in 2%. Reproducibility of the 3 ETDRS evaluations was comparable with a weighted κ value of 0.57 with standard 7-field imaging, 0.65 with 7-field UWF imaging, and 0.60 with global ETDRS scale imaging. CONCLUSIONS: Moderate agreement was found in the ETDRS DR severity scale between standard 7-field and UWF imaging, indicating caution in interchanging data from the 2 methods. Both methods showed good reproducibility for clinical trial outcome of 2-step change. The global ETDRS scale provides a comprehensive score to incorporate peripheral changes into the ETDRS scale. The implications of the global scale on progression rate are yet to be determined.