Colour slides or digital photography in diabetes screening - a comparison

Purpose: The aim of this study was to compare digital images with slides in detecting and grading diabetic retinopathy, and to assess the retinopathy screening performed by ophthalmic nurses. Method: 283 consecutive patients were examined using digital colour and red-free photography (Topcon Imagenet System 1.53) and 35 mm slides (Topcon TRC-50 VT fundus camera, Kodachrome 64 colour film). The images were graded by the worst eye according to the Wisconsin classification by an ophthalmologist and ophthalmic nurse independently Results: There was exact agreement between grades obtained from the colour slides and the digital colour images in 82% (weighted kappa 0.88; 95% CI 0.80-0,96), and in 85% when redfree images were used as an adjunct to the digital colour images, There was a tendency towards undergrading of the digital colour images and overgrading of the digital redfree images, compared with the colour slides, Inter- and intragrader agreement (weighted kappa) varied between 0.77 and 0.84 for digital photography and between 0.88 and 0.90 for colour slides, Conclusion: Good to excellent agreement was found between the grading of colour slides and digital colour images, the latter, however, associated with a slightly lower reliability. The adjunct of redfree images seemed to facilitate the detection of retinopathic lesions.