Grading diabetic retinopathy severity from compressed digital retinal images compared with uncompressed images and film

Purpose: To compare research grading of diabetic retinopathy (DR) severity level from compressed digital images versus uncompressed images and film. Methods: Compressed (JPEG2000, 37:1) digital images (C) were compared with uncompressed digital (U) and film (F) stereoscopic photographs from a 152-eye cohort with full-spectrum Early Treatment Diabetic Retinopathy Study severity levels for agreement on severity level, DR presence with ascending severity threshold, presence of DR index lesions, and repeatability of grading. Results: Classification of Early Treatment Diabetic Retinopathy Study severity levels from C images agreed substantially with results from F images (κ = 0.60, κw [linear weighted] = 0.86) and uncompressed digital images (κ = 0.76, κw = 0.92). For agreement of uncompressed digital versus F images, κ = 0.62 and κw = 0.86. Distribution of Early Treatment Diabetic Retinopathy Study levels was not significantly different between C and F images (P = 0.09, Bhapkar's test for marginal homogeneity). For presence/absence of DR at 8 ascending severity thresholds, agreement between C and F was "almost perfect" (κ ≥ 0.8). Agreement on severity level between readers with C images was at least as good as that with uncompressed digital image or F. Repeatability of severity threshold grading between readers was similar using C or F images. For identifying individual DR lesions, agreement between C and F ranged from "moderate" to "perfect." Agreement of grading venous beading from C was slightly lower than from F. Conclusion: Full Early Treatment Diabetic Retinopathy Study scale DR severity level grading using C images is comparable to that using U images or film.