Comparison of film and digital fundus photographs in eyes of individuals with diabetes mellitus

Abstract

Purpose: To compare grading of diabetic retinopathy (DR) and diabetic macular edema (DME) from stereoscopic film versus stereoscopic digital photographs obtained from a subset of Diabetic Retinopathy Clinical Research Network (DRCR.net) participants.

Methods: In this photographic media comparison study, digital and film images were obtained at a single study visit from some of the subjects enrolled in active DRCR.net clinical study protocols. Digital camera systems and digital and film photographers were certified to obtain images according to standard procedures. Images were graded for DR severity and DME in a masked fashion by Fundus Photograph Reading Center (Madison, WI) graders. Agreement between gradings was assessed by calculating the percentage of agreement and κ statistics.

Results: Images obtained with both film and digital media were submitted for 155 eyes of 96 study participants. On a nine-step Early Treatment Diabetic Retinopathy study DR severity scale, grading agreed exactly in 74%, and was within one step of agreement in 93%, with a weighted κ statistic of 0.82 (95% confidence interval [CI], 0.71-0.92). On a nine-step DME severity scale and three-step clinically significant macular edema (CSME) scale, grading agreed exactly in 39% and 88%, respectively, and within one step in 70% and 92% (weighted κ statistic, 0.44 [95% Cl, 0.34-0.54] and 0.72 [95% Cl, 0.55-0.90], respectively).

Conclusions: Among clinical sites participating in the DRCR.net, agreement between film and digital images was substantial to almost perfect for DR severity level and moderate to substantial for DME and CSME severity levels, respectively. Replacement of film fundus images with digital images for DR severity level should not adversely affect clinical trial quality. (ClinicalTrials.gov numbers, NCT00367133, NCT00369486, NCT00444600, NCT00445003, NCT00709319.)