Identification of diabetic retinopathy by stereoscopic digital imaging viateleophthalmology: a comparison to slide film

Background: Diabetic retinopathy is a leading cause of vision loss in North America, We compared mydriatic seven-field stereoscopic digital imaging to 100 ASA slide film photography for the identification of diabetic retinopa thy via teleophthalmology. Methods: Patients from a northern Alberta community with diabetes mellitus diagnosed by a physician were asked to participate in a teleophthalmology p ilot project. Patients were enrolled at four different times between Octobe r 1999 and June 2000, Seven 30 degrees fields of the retina were photograph ed with both slide film and digital imaging (resolution 2008 X 3040 pixels) through a dilated pupil. Slide film was developed and reviewed in a masked fashion by a retinal specialist. Digital images for each patient were tran smitted by satellite to Edmonton and analysed a minimum of 2 months after t he original slide film. Retinal abnormalities were graded with the use of t he Early Treatment Diabetic Retinopathy Study extension of the modified Air lie House classification. We calculated the sensitivity and specificity of digital imaging for the identification of features of diabetic retinopathy as seen on slide film. Pearson's correlation coefficient was also calculate d. Results: A total of 121 patients (241 eyes), of whom 114 (94.2%) had non-in sulin-dependent diabetes, participated in the study. The average duration o f diabetes was 8.5 years. Of the 121 patients 57 (47.1%) had diabetic retin opathy, 12 (9.9%) had clinically significant macular edema and 2 (1.6%) had neovascularization, Pearson's correlation coefficient for the presence of retinopathy between slide film and stereoscopic digital imaging was 0.92 fo r microaneurysms, 0.80 for hemorrhages, 0.45 for intraretinal microvascular abnormalities, 0.32 for venous beading, 1.00 for neovascularization of the disc,1.00 for neovascularization elsewhere in the retina and 0.97 for clin ically significant macular edema (p < 0.001). The correlation between the t wo techniques for severe nonproliferative diabetic retinopathy (NPDR) was 0 .86 and for high-risk proliferative diabetic retinopathy 1.00 (p < 0.001). Interpretation: Stereoscopic digital imaging has a high level of correlatio n with slide film for the identification of most features of diabetic retin opathy, including microaneurysms, hemorrhage, severe NPDR, highrisk prolife rative diabetic retinopathy and clinically significant macular edema.